The role of civilian roll-on/roll-off (RO-RO) ferries in a PLA invasion of Taiwan deserves its growing notoriety. With port access secured or coupled with developing logistics over the shore capabilities, RO-RO ferries could deliver significant volumes of forces across the Taiwan Strait, offsetting shortfalls in the PLA’s organic sea lift.1 Some analysts have even described mobilized civilian assets like RO-ROs as a “central feature of [the PLA’s] preferred approach” to a cross-strait invasion.2
But the PLA appears intent on assigning RO-RO ferries to another mission: launching amphibious combat forces directly onto beaches from offshore. The PLA has long lacked sufficient landing ships to deliver its full complement of amphibious assault forces, from both army and Navy Marine Corps forces, in the initial assault landing on Taiwan. Rather than building numerous grey-hulled traditional landing ships, the addition of RO-RO ferries into a combined landing ship fleet could quickly close this gap.
To make this possible, the PLA has been modifying RO-RO ferries with new stern ramps enabling in-water operations to launch and recover amphibious combat vehicles. The first publicly demonstrated use of the new ramps occurred in 2019 during an exercise involving the 15,560-ton RO-RO ferry Bang Chui Dao, owned and operated by COSCO Shipping Ferry Company and a regular vessel supporting military transportation training exercises. Other ferries have received similar modifications, giving the PLA a significant boost in the total volume of amphibious lift the PLA could muster in a cross-strait amphibious landing.3 This expansion in PLA amphibious capabilities has generated very little attention by the international media despite its clear purpose.
Amphibious warships are optimized for launching and recovering amphibious combat forces, including swimming armor. They feature well decks closer to the waterline, sometimes submersible, making it easier for forces to launch or recover out of the water. The above image depicts a ZBD-05 approaching the LST Wan Yang Shan’s (No. 995) stern gate and illustrates the challenge of RO-RO ferries in conducting amphibious launch and recovery, which feature freight decks much higher above the waterline that are suited to the height of quay walls. Providing ramp strength that can span that distance requires strong hydraulic rams and stays.
COSCO Shipping Ferry Co., Ltd.
The Bang Chui Dao belongs to COSCO Shipping Ferry Co., Ltd., under the state-owned shipping conglomerate COSCO, which operates ten large passenger RO-RO ferries in the Bohai Gulf. COSCO Shipping Ferry has provided service for PLA transportation support for over 25 years.5 It continues to provide its vessels as a “transport group” (海运大队) of the PLA’s strategic projection support shipping fleet (战略投送支援船队), one of many organized within COSCO businesses and other major commercial shippers to support PLA transportation requirements.6
COSCO Shipping Ferry Co. has been developing capabilities for offshore amphibious launch for its ferries over a number of years. In 2016, the company reported having installed a number of new features into four of its ferries, in response to new national defense requirements. The report suggested the Long Xing Dao and the Yong Xing Dao were among the modified vessels, built in 2010 and 2011 respectively. Noted modifications included rapid egress corridors for personnel and some small equipment, measures in compartment design to resist sinking when damaged, and new hydraulically driven systems to enable greater stern ramp extension for moving amphibious armor on and off the vessel at sea.7
The Yong Xing Dao, Long Xing Dao, Hu Lu Dao and the Pu Tuo Dao have each had their stern ramps upgraded within the past couple of years. These ramps likely utilize the same mechanical principle behind that used for the Bang Chui Dao. Structurally, they appear stronger, longer, and are actuated by heavier-duty hydraulic rams. Noticeably, the ramps are flanked by large, multi-hinged steel support arms that act as preventer stays to maintain ramp rigidity when under tension by the hydraulic rams. These are mounted externally as shown below. The Bang Chui Dao’s ramp-mounted hydraulic assemblies had similar preventers but were mounted internally due to the lack of room between the stern ramp and the quarter-stern ramp.
Some modified ramp systems will not be permanent installations. For example, recent public footage of the Bang Chui Dao indicates the ramp featured in the 2020 PLAN Marine Corps exercise was removed, and the regular commercial service ramp reinstalled. While suited for launching amphibious armor, the modified system clearly reduced the horizontal clearance of the stern ramp and would not be practical for commercial operators that need to accommodate various sizes of vehicles and trucks. Thus, the PLA likely has these systems held in storage to be installed on vessels like the Bang Chui Dao and the Hai Yang Dao, which features the same quarter-stern ramp, when needed.
Observations of vessel activities also indicate additional COSCO ferries have been similarly modified. In two recent reports, Michael J. Dahm found the Hu Lu Dao took part in amphibious landing training exercises in July 2021, and the Chang Shan Dao in July 2022.8 This implies at least seven COSCO passenger RO-RO ferries have the ability to conduct offshore launch of amphibious combat forces.
Conversions to BH Ferry Group
Ramp conversion practices have matured enough for wider application in other companies. This is evident within the Bohai Ferry Group, a RO-RO shipping company also concentrated in the Bohai Gulf and comprising the Eighth Transport Group.9
Over the last 15 years, Bohai Ferry Group has expanded its fleet and its cooperation with the PLA.10 The company began implementing national defense requirements in new vessel construction when the former Jinan Military Region Military Transportation Department participated in the design of the 36,000-ton class of ferries starting in 2010 with the Bohai Cuizhu. With inputs from regional military units regarding equipment requirements, the new ferries received helicopter pads, reserve medical spaces, improved command and communications equipment, greater freight deck ventilation, improved firefighting systems and other features.11 While some modifications are difficult to observe directly, some of the latest ramp conversions are readily apparent.
At some point in the last two years, Bohai Ferry Group modified the stern ramps on four of its 36,000 gross-ton ferries, the Bohai Mazhu, Bohai Cuizhu, Bohai Jingzhu, and Bohai Zuanzhu. Specifically, large hydraulic assemblies have been installed on the transom flanking the stern ramp. Similar to the Bang Chui Dao’s assembly, heavy-duty hydraulic cylinders will be released from their secured positions and assisted via a smaller hydraulic ram into a set of clevis brackets affixed to the ramp. As designed, this new position allows for further depression of the ramp into the water, and thus the launch of amphibious combat vehicles.
These new systems are also operational in recent PLA amphibious exercises, deploying and recovering amphibious forces from offshore, as documented by Dahm. Participation of all four of the 36,000 gross ton class, as well as the 24,777 gross ton multi-purpose ferry Bohai Hengtong was observed in late summer exercises of 2021 and 2022.13 The Bohai Hengtong’s stern ramp is likely long enough for amphibious launch, but may require additional ramp-mounted support due to the presence of the vessel’s quarter-stern ramp. The specific ramp modification for this vessel or its sister ship the Bo Hai Heng Da is unclear.
These modifications to civilian RO-RO ferry ramps have the potential to significantly augment the PLA’s access to amphibious lift. The ferries previously identified contain the following lane in meter (LIM) dimensions and deadweight tonnage (DWT – i.e., a ship’s total carrying capacity) which can help analysts determine the total volume of amphibious combat forces they can add to the PLAN’s organic amphibious lift.
RO-RO Ferries Likely Capable of Offshore Amphibious Launch/Recovery (as of February 2, 2023)
Bohai Cuizhu (渤海翠珠)
Permanent external installation
Bohai Jingzhu (渤海晶珠)
Permanent external installation
Bohai Mazhu (渤海玛珠)
Permanent external installation
Bohai Zuanzhu (渤海钻珠)
Permanent external installation
Bohai Hengtong (渤海恒通)
Yong Xing Dao (永兴岛)
Long Xing Dao (龙兴岛)
Chang Shan Dao (长山岛)
Likely permanent installation
Pu Tuo Dao (普陀岛)
Hu Lu Dao (葫芦岛)
Bang Chui Dao (棒棰岛)
Requires internally-mounted system
Hai Yang Dao (海洋岛)
Requires internally-mounted system
Note: Most of the modified vessels included in this table have been visually confirmed through openly available imagery and video sources online.
While simply dividing each vessel’s deadweight tonnage by vehicle weights can yield hundreds of vehicles per vessel, the impressive advertised carrying capacities of these ships do not translate directly into the volume of PLA forces they can transport. Crew, passengers, fresh water, fuel, and other various cargo will take up some of the deadweight tonnage listed above, and the remainder will be portioned out to vehicles, as permitted by the total vehicle lane space. Other basic characteristics such as the spacing of vehicle tie down anchor points in vessel decks will also be important factors in determining capacity.
Internal spatial dimensions and freight deck strength will better determine what kind of vehicle and how many can load. PLA transportation experts find that most of China’s RO-RO passenger ferries feature 3.1-meter wide vehicle lanes, which do not satisfy the width requirements for large numbers of tracked armored vehicles. In addition to not optimizing occupied deck space, improper positioning of heavy loads outside of vehicle lanes could also result in damage to freight decks. Additional internal clearance constraints along ramps and elevators will also limit what types of vehicles and cargo are stowed on each deck, likely only permitting the heaviest armored vehicles, such as main battle tanks, on the main freight decks.14 For example, the four 36,000-gross ton Bohai Ferry Group ferries each have 2,500 total LIM. Despite this impressive volume, PLA experts have noted limitations in their ability to carry large, armored vehicles.
The Bohai Mazhu, the last of the four to enter operation in April 2015, has internal ramp widths of 3.5m and elevator widths of 3m, limiting heavy tanks to only the main freight deck.15 It is likely the Bohai Mazhu’s preceding sister ships also feature the same limiting dimensions. These issues impact transport of the PLA’s heaviest equipment but could also limit their ability to transport amphibious combat vehicles such as the Type-05 series of vehicles. Boat-like in its hull design, a ZBD-05 has a reported width of 3.36 meters and length of 9.5 meters, which could cause difficulty in making turns and accessing upper or lower decks.16 Other vessels may be more accommodating. For example, the Chang Shan Dao reportedly has a 3.6 m-wide elevator and 3.5 m-wide internal ramps, as may its sister ships, the Yong Xing Dao and Long Xing Dao.17
More importantly, while total loading capacities may be useful for gauging how the PLA might optimize its loading plans for relatively secure terminal to terminal delivery operations, offshore amphibious launch entails very different considerations. The stowage of amphibious combat forces will likely be done according to combat loading plans that do not emphasize the maximization of forces occupying deck space. Instead, forces would load according to their assigned assault waves, which likely include both armor and infantry aboard assault craft, and other support elements. Each wave must be positioned and readied to access and launch from the vessel’s stern ramp.
Moreover, launching amphibious combat forces brings vessels closer to active combat areas. The threat of adversary attacks could lead the PLA to disperse forces across many ships. Multiple units confined to a single ferry could be a vulnerability demanding more protection of that single vessel. It is likely that ferries participating in this mission will not be loaded to the brim. As pure transporters, they may seek to launch forces as quickly as possible to reduce their own exposure and swiftly return to ports of embarkation to load follow-on forces.
Despite this, these vessels offer a significant additional source of amphibious lift for the PLA, especially for delivery of first echelon amphibious combat forces critical to securing areas for landing the follow-on invasion force. With the previously-mentioned spatial limitations in mind, a conservative estimate of the total capacity of the ships identified in this article adds on capacity sufficient for half the PLA army’s primary amphibious combat forces (12 amphibious combined arms battalions).18 This places one battalion on each vessel, with room for additional supporting elements from their respective brigades. Depending on internal space constraints, vessels like the Pu Tuo Dao could probably deliver a single battalion, while some of the larger vessels could likely carry up to two battalions if the PLA accepts the risk. Having fewer forces embarked would also make it easier for these vessels to support forces loaded well in advance of an invasion, as many ferries market to tourists their berthing compartments complete with toilets and showers, and feature mess halls and recreational facilities. Spare vehicle deck space could also be employed to support embarked amphibious units. If done right, such early loading could relieve pressure on PLA loading operations, but also make detecting a force build up more difficult.
The PLA has rapidly expanded its landing ship fleet over the last few years. It has not taken the form many may have expected, such as the construction of numerous naval landing ships, instead focusing efforts on civilian RO-RO ferries to fulfill the PLA’s requirements. This article set out to identify the PRC-flagged RO-RO ferries with ramps that can enable offshore amphibious launch. It has likely failed to enumerate all the various ramp configurations and identify all the vessels involved.
Both COSCO Shipping Ferry Group and Bohai Ferry Group have ferries capable of supporting this mission. Some ramp systems are temporary, suggesting preparations for some ferries to rapidly refit when needed, while others are permanent observable installations. The ferries themselves are dual-commercial and military use ships, however, their ramp modifications have a sole purpose, the offshore launch of amphibious combat forces in a landing operation against Taiwan. Furthermore, these capabilities are not simply theoretical, as some of these ships take part in landing exercises with PLA amphibious ground units.
The PRC appears to have significantly expanded its amphibious lift capacity with little notice from the international community, much less criticism. While many PLA experts write openly on the important roles of the commercial RO-RO fleet in a cross-Strait invasion, specifically their roles in transporting large volumes of heavy follow-on forces, they have generally steered clear of discussing their role in offshore amphibious launch. If these RO-RO modifications and their application in military exercises are observable by a foreign audience, they should be readily known by PLA military transportation professionals. This supports the author’s original assertion in 2021 that this expansion in capacity could occur quickly and quietly.
There are still many more questions to be answered regarding the effectiveness of this approach. The PLA must tackle coordination between the joint forces, including organic landing ships and civilian assets. There are organizational, command and control, communications, security, and numerous other issues to solve before RO-RO ferries can effectively support a joint island landing campaign, especially if they are to join in delivering landing assault waves. Nonetheless, an initial understanding of the scale of this approach is important for gauging the significance of its contribution toward delivering the PLA’s joint landing forces.
Conor Kennedy is a research associate in the U.S. Naval War College’s China Maritime Studies Institute in Rhode Island.
The analyses and opinions expressed in this paper are those of the author and do not necessarily reflect those of the U.S. Navy or the U.S. Naval War College.
1. For an analysis of a PLA invasion against port locations, see: Ian Easton, Hostile Harbors: Taiwan’s Ports and PLA Invasion Plans,” Project 2049 Institute, July 22, 2021, https://project2049.net/2021/07/22/hostile-harbors-taiwans-ports-and-pla-invasion-plans/; For an analysis of PLA logistics over the shore capabilities, see: Dahm, J. Michael, “China Maritime Report No. 16: Chinese Ferry Tales: The PLA’s Use of Civilian Shipping in Support of Over-the-Shore Logistics” (2021). CMSI China Maritime Reports. 16. https://digital-commons.usnwc.edu/cmsi-maritime-reports/16; and “China Maritime Report No. 25: More Chinese Ferry Tales: China’s Use of Civilian Shipping in Military Activities, 2021-2022” (2023). CMSI China Maritime Reports. 25. https://digital-commons.usnwc.edu/cmsi-maritime-reports/25.
2. Henley, Lonnie D., “China Maritime Report No. 21: Civilian Shipping and Maritime Militia: The Logistics Backbone of a Taiwan Invasion” (2022). CMSI China Maritime Reports. 21. https://digital-commons.usnwc.edu/cmsi-maritime-reports/21.
3. Conor Kennedy, “Ramping the Strait: Quick and Dirty Solutions to Boost Amphibious Lift,” China Brief, Volume 21, Issue: 14, https://jamestown.org/program/ramping-the-strait-quick-and-dirty-solutions-to-boost-amphibious-lift/.
4. 严家罗, 周紫春, 周启青 [Yan Jialuo, Zhou Zichun, Zhou Qiqing], 海军陆战队某旅海上浮渡装卸载训练 [“A Navy Marine Corps Brigade in Afloat Loading and Unloading Exercises”], 当代海军 [Navy Today], No. 7, 2015, p. 31.
5. 潘诚, 王正旭 [Pan Cheng, Wang Zhengxu], 沈阳联勤保障中心某航务军代处与企业共同制定军运细则 [“A Shenyang Joint Logistics Support Center Navigational Military Representative Office Jointly Formulates Military Transportation Rules with an Enterprise”], 中国国防报 [China Defence News], June 15, 2017, p. 3, http://www.81.cn/gfbmap/content/21/2017-06/15/03/2017061503_pdf.pdf.
6. Conor M. Kennedy, “China Maritime Report No. 4: Civil Transport in PLA Power Projection” (2019). CMSI China Maritime Reports. 4. https://digital-commons.usnwc.edu/cmsi-maritime-reports/4.
7. 王正旭, 高勇, 贾文暄 [Wang Zhengxu, Gao Yong, Jia Wenxuan], 客轮首尾开门运兵运超重军事装备 可起降直升机 [“Passenger Ships Carry Troops and Overweight Military Equipment, and Can Land Helicopters”], 中国国防报 [China Defence News], September 29, 2016, https://www.chinanews.com.cn/mil/2016/09-29/8018481.shtml.
9. 李远星, 王丙 [Li Yuanxing, Wang Bing], 新时代战略投送支援力量建设运用研究 [“Research on Construction and Use of Strategic Projection Support Forces in the New Era”], 国防 [National Defense], No. 12 (2017), 20–23.
10. Since 2006, Bohai Ferry Group has constructed over 16 large RO-RO ferries ranging from 20,000 to 45,000 gross tons. See: 关于我们 [“About Us”], 渤海轮渡集团股份有限公司 [Bohai Ferry Group Co., Ltd.], Undated, http://www.bhferry.com/brief.html
11. 李响 [Li Xiang], 军民融合领域的一次成功实践: “渤海翠珠” 滚装船提升我军海上战略投送能力纪实 [“Record of a Successful Practice in Civil-Military Fusion: the RO-RO Ship ‘Bohai Cuizhu’ Enhances Our Military’s Maritime Strategic Projection Capabilities”], 国防科技工业 [National Defense Science and Technology Industry], No. 1 (2012), 53.
12. 建设打仗后勤 [“Building Warfighting Logistics”], CCTV –《追光》[CCTV- Chasing the Light], Episode 11, October 9, 2022, https://tv.cctv.com/2022/10/09/VIDErLF38LiQWiL4DD2eu0UM221009.shtml?spm=C55953877151.PmHVnEZCnjLh.0.0
13. Dahm, “China Maritime Report No. 16,” pp. 33-39; Dahm, “China Maritime Report No. 25,” pp. 36-44; For an image depicting the Bo Hai Heng Tong launching vehicles, see: H I Sutton and Sam LaGrone, “Chinese Launch Assault Craft from Civilian Car Ferries in Mass Amphibious Invasion Drill, Satellite Photos Show,” USNI News, September 28, 2022, https://news.usni.org/2022/09/28/chinese-launch-assault-craft-from-civilian-car-ferries-in-mass-amphibious-invasion-drill-satellite-photos-show
14. 孙琪, 刘宝新 [Sun Qi, Liu Baoxin], 民用客滚船军事应用研究 [“Research on Military Application of Civil Ro-Ro Passenger Ships”], 军事交通学报 [Journal of Military Transportation], No. 2, 2022, p. 26.
17. 吴克南 [Wu Kenan], 我国滚装船运输军事重装备的适用性研究 [“The Applicability Research of China Ro-Ro Ship Used to Transport Military Heavy Equipment”], 大连海事大学-硕士学位论文 [Dalian Maritime University – Master’s Thesis], March 2016, p.
18. This is based on the estimated size of an army amphibious combined arms battalion consisting of 80 vehicles and 500-600 troops. See: Blasko, Dennis J., “China Maritime Report No. 20: The PLA Army Amphibious Force” (2022). CMSI China Maritime Reports. 20, pp. 3-4. https://digital-commons.usnwc.edu/cmsi-maritime-reports/20.
Featured Image: A CCTV report showed a cargo ship that was being used to carry troops, weapons and supplies in a recent PLA exercise. (Photo via CCTV)
A recent article published by the Center for International Maritime Security (CIMSEC) – the first in a series – does an outstanding job of describing and explaining the Navy’s “core operating concept” of Distributed Maritime Operations (DMO). In short, DMO calls for “…the massing and convergence of fires from distributed forces, complicating adversary targeting and decision-making, and networking effects across platforms and domains.”1
The strike effectiveness of the DMO operating concept requires further investigation. In pursuing this, it is important to recall that a fleet does four things – it Scouts, it Screens, it Strikes, and it Bases.2 As currently envisioned, at least in open source definitions, DMO is not yet well-developed in the Scouting, Screening, and Basing functions of a fleet. Rather, DMO seems mostly focused on the offensive functions of a fleet, the Strike function.
The first step in this analysis will be to analyze a traditional concentrated force versus another concentrated force using the salvo equations. The second step will be to look at a distributed force that is able to mass fires against a concentrated force. The final step will be to look at a concentrated force that engages part of a distributed force. We will also look at what “firing effectively first” means in practice, and what happens if the enemy force distributes.
“how modern naval combat follows a salvo model: opponents apply a pulse of combat power to each other in an instantaneous salvo exchange. A salvo exchange is an interaction of offensive combat power (e.g., mines, torpedoes, bombs, or missiles) and defensive combat power (e.g., surface-to-air missiles [SAMs], jamming, chaff, decoys). Combat power remaining from these interactions is applied against a target’s staying power (the number of hits of a particular weapon that a target can withstand and still be useful for combat purposes).”3
The salvo equations are presented here for reference:
Concentrated versus Concentrated
The first step in our analysis will be to look at two concentrated forces engaging one another. To simplify the analysis, it is assumed that each force is exactly equal, where each force consists entirely of the same number of missile-equipped surface ships, with the same offensive and defensive capabilities. These include:
Each force consists of six surface ships (A = B = 6).
Each surface ship has a displacement of 8,000 tons. Using the “cube root rule,” this means that it takes two “thousand-pound bomb equivalents” (TPBEs) to put a ship out of action. Given the destructive force of modern explosives, that equates to 2 x 660 lbs, or 1,320 lbs of modern warhead explosives. Assuming a warhead size of 500 lbs, it would take 2.64 warheads to put an 8,000 ton ship out of action. (a1 = b1 = 2.64).4
Each surface ship is equipped as follows:
Eight anti-ship cruise missiles (ASCMs) equipped with a 500 lb warhead. All ASCMs are considered to be “well-aimed” (i.e., unless otherwise destroyed, decoyed, or defeated, the ASCM would hit its intended target; this is not always true, as discussed in Chapter 1 of Fighting the Fleet.5 b = ).
A surface-to-air missile (SAM) system capable of destroying two incoming ASCMs in a general engagement involving multiple incoming missiles.
A close in weapons system (CIWS) capable of destroying two incoming ASCMs.
An electronic countermeasure system (ECM) capable of defeating one ASCM.
A decoy system capable of defeating one ASCM.
Therefore, given the combined capabilities of the SAM, CIWS, ECM, and decoy systems to destroy or defeat incoming ASCMs, a3 = b3 = 6.
Each force has equivalent organic and inorganic scouting capabilities, and is able to detect and localize the opposing force at the maximum range of their ASCMs.
Based on these assumptions, the salvo equations for an engagement between two concentrated forces are featured in Figure 1:
Predicting damage to warships in combat is always difficult, but a change in the number of units in force A and B () of 4.55 indicates enough hits to put 4.55 ships out of action in each force.6 Of course, this is highly dependent on hit distribution, which, if evenly distributed across the force, would mean that each ship in each force received some damage, but was not put out of action. In addition, this scenario assumes that each force was able to launch an attack “simultaneously,” where simultaneity is defined as each force being able to launch its ASCMs against the other force before it is hit by the other force’s ASCMs.
The essence of Captain Wayne Hughes’s admonition to “fire effectively first” then is to launch an attack and have missiles hit the opposing force before that force can launch its missiles.17 Assume that if force B was able to “fire effectively first,” then proceeding from the salvo equations above, force A would be reduced by a total of 4.55 ships, so force A’s subsequent attack on force B would result in the following:
A negative number for DB indicates that the B force is likely to be able to defeat all of force A’s incoming missiles; and the bigger the number, the more likely it will defeat the incoming strike. Such is the advantage of being able to “fire effectively first.”
This highlights two other aspects of offensive and defensive fires. First, close-range defensive fires such as point-defense missiles can often be replenished prior to another salvo attack. While they may be limited in their ability to defeat an incoming salvo, they can generally be reloaded and prepared to defend against a future salvo, without any reduction in capability. Second, this is not always true of ASCMs, many of which are housed in dedicated launchers and are limited in number and cannot be reloaded quickly or at sea. As the reader will see in this example, there is arguably little incentive to retain offensive fires for possible future engagements, as it often takes all the offensive firepower available to overcome the opponent’s defensive capability.
Distributed versus Concentrated
The second step in this analysis is to look at a distributed force that is able to mass its fires against a concentrated force. However, at this point the reader should be able to see that the results are likely to be similar as in the scenario presented above, assuming that the concentrated force is able to launch against all elements of the distributed force. An issue associated with the distributed force is the coordination required for a distributed force to mass its fires against a common target. Scouting information about target location, course, and speed would need to be communicated to all elements of the distributed force, and some sort of coordination and communication would need to occur for the distributed elements to mass their fires against the target. This is inherently more complex than attacking with a concentrated force, and more subject to communication and coordination failure.
The third step in this analysis is to look at a concentrated force that engages part of a distributed force. The danger in distributing one’s own force in the face of a competent – or lucky – opponent is that the opposing force will defeat one part of own force “in detail”; that is, the entire opposing force will engage just part of own force and be able to destroy it. Assuming that force A divides itself into two equal parts, A(1) and A(2), and assuming that force B engages A(1) before A(2) can become involved in the fight, such an engagement is characterized in the salvo equations as depicted in Figure 3:
Here we see that force B has a preponderance of offensive firepower that overwhelms A(1)’s defensive capability, and force B’s defensive capability is able to defeat force A(1)’s inadequate offensive punch. Should A(2) get off a shot against force B, its results would look exactly like those of force A(1), as shown in Figure 4:
The net result of the damage to force A in the distributed case would be the likely destruction of all three A(1) ships, with no damage to the opposing A(2) ships. Recall that in the concentrated case, the damage to force A ships (i.e., 4.55 put out of action) would be distributed over the six ships of the force. Here, however, enough offensive power from force B to put 11.36 ships out of action would only be distributed over the three ships of force A(1), virtually ensuring that all three ships would be put entirely out of action. Force B would not suffer any damage at all. Compare this to the concentrated case or the case where a distributed force A had been able to mass its fires (Figure 1), where force B would have suffered an equal amount of damage.
What happens if force B only detects one of the distributed parts of force A (force A(1)), but distributed force A is able to mass its fires against force B?
The result is depicted in Figure 5. All three ships of force A(1) would likely be put out of action, no damage would be incurred by force A(2), and force B would incur the same damage as if force A were concentrated. It turns out this is the one case where a distributed force has a strike advantage over a concentrated force. However, it should be noted that this is not an advantage conferred by distribution, it is an advantage conferred by effective Screening and Scouting. One part of the distributed force drew the attention and the fire of the concentrated force, but was able to combine its fires with the undetected portion of the distributed force.8
Next, what would happen if force B knew that force A had distributed itself, it had detected force A(1), and it assumed that force A(2) was nearby? If it retained half of its ASCMs for a possible future engagement with force A(2), the engagement with A(1) might look like the results contained in Figure 6:
Of course, a future engagement with force A(2) would look much the same, and note that force B does not suffer any damage. Given the uncertainty of combat, it makes much more sense for force B to launch all of its ASCMs against force A(1), likely destroying all of force A(1), and use screening to scuttle back into port before any other force can attack it – a classic case of Corbett’s “arrested offense.”
“Fire Effectively First!”
In Figure 2, the value of firing effectively first was illustrated for the base case of two concentrated forces engaging one another. This also applies to a concentrated force and a distributed force that engage each other simultaneously. The following looks at the value of “firing effectively first” for two of the other cases discussed previously:
A concentrated force that engages part of a distributed force (Figure 7). It should be self-evident that if the concentrated force, B, fires effectively first, the engaged part of the distributed force will be put out of action. But what happens if the part of the distributed force A(1) fires effectively first against the concentrated force B, and then B launches an attack on A(1)? As we can see in the following equations, B is able to defeat A(1)’s incoming salvo, and since it is undamaged, if it is able to launch an attack against A(1), it will overwhelm A(1)’s defenses.
A concentrated force only detects one of the distributed parts of force A (Figure 8). In this case, force B fires effectively first against force A(1), which is put out of action, and force A(2) launches a retaliatory strike against force B. A(1) is destroyed, and force B is able to defeat A(2)’s inadequate attack.
Whether a force distributes or not, what is essential to victory – and survival – is the ability to “fire effectively first,” and firing effectively first is a function of scouting, not distribution or concentration of platforms. That being said, even if the distributed force fires first, it will be unable to defeat or even damage the concentrated force unless it can effectively coordinate its attack.
What if the Enemy Distributes?
If distribution is a good idea, then we must expect the other side to distribute as well. The combinations of possible engagements begin to escalate quickly, depending on how each side distributes its forces. We can, however, look at some of the more interesting cases, based on the assumption that each side distributes evenly into two equally-sized groups of three ships:
Both forces are able to launch coordinated attacks on each other near-simultaneously. The results will be the same as those depicted in Figure 1. Both sides being distributed provides no advantage to either side in terms of strike.
One force is able to attack one part of the other force, but the entire other force is able to attack both parts of the first force. The results will be the same as those depicted in Figure 5. Both sides being distributed provides no advantage to either side in terms of strike.
These dynamics yield a set of recommendations, including:
No matter how forces are deployed – concentrated, distributed, or some other way – win the scouting contest and “fire effectively first.”
If forces are distributed but the communications capability is not able to coordinate their fires, then force posture must be rearranged to respect the limits of communication. If this cannot be done in time, then better to disengage to fight another day.
Improve screening. Decoys, for example, can be very useful in diluting the effect of the enemy’s salvo. The effect of each ship in force A being able to decoy just one more missile each is shown in Figure 9: it effectively halves the amount of damage force A could expect to receive.
The salvo equations are analytical tools, not predictive ones. They do not result in “the answer” as to exactly how any single engagement will turn out. Combat entropy and instability, discussed at length in Fighting the Fleet, is a factor worth appreciating, such as how six bombs sunk four carriers at Midway, but five kamikazes did not sink one destroyer, USS Laffey, at Okinawa.9 That being said, the salvo equations can be used as an analytical tool to provide insight into probable outcomes. As they say, the race does not always go to the fastest, or the contest to the strongest, but that is the way to bet.
It should be noted that the single point of failure for a distributed force is the ability to coordinate a strike on another force. This coordination becomes even more complex with greater distribution of one’s own force, and even more so when the other force is distributed.10 If the distributed force cannot coordinate their fires then they lose in every scenario. This may be caused by jamming or some other interruption of communications, but it could also be from any failure to efficiently coordinate a strike, which could be as simple as poor distribution of weapons, training shortcomings, and other shortfalls.
The one case where a distributed force comes out ahead of a concentrated force is the case where only one part of the distributed force is detected by the enemy and absorbs the enemy’s attack, but is able to combine its strike with the other part of the distributed force before it dies. But that is not a “concept of operation,” it is more of a scouting tactic, and in prior generations this was better implemented with a LAMPS Mk III, Hawklink, and the naval tactical data system (NTDS).
DMO might be able to “complicate adversary targeting and decision-making” and it should be noted it would apply to one’s own force if the enemy distributes as well. But when it comes to the Strike function of a fleet, a distributed force had better be able to efficiently mass its offensive fires, or it runs the risk of being defeated in detail, resulting in, at best, a disappointing exchange in the number of destroyed and damaged ships.
 Cares and Cowden, p. 23. Estimating the number of hits to put a ship out of action is probably the most controversial aspect of using the Salvo Equations. The reader is invited to substitute whatever value they desire and conduct the analysis themselves. One useful approach is to use a parametric range of values and discover the sensitivity of the force to the number of hits required.
 Cares and Cowden, pp. 19-22
 How to interpret the Salvo Equations, as well as the concept of “Combat Entropy”, is discussed extensively in Chapter 1 of Fighting the Fleet.
 Hughes, Captain Wayne P., USN (Ret.) and Rear Admiral Robert P. Girrier, USN (Ret.), Fleet Tactics and Naval Operations, Third Edition (Annapolis, MD: Naval Institute Press, 2018), Chapter 13.
 Quick show of hands: who wants to serve in force A(1)?
 Cares and Cowden, pp. 19-22
 Distributed networked operations can become amazingly complex. Those interested in the theory and application of distributed network operations are invited to read Cares, Jeff. Distributed Network Operations: The Foundations of Network Centric Warfare. Newport, RI: Alidade Press, 2005.
Featured Image: Amphibious assault ship USS Bonhomme Richard (LHD 6) fires a NATO Sea Sparrow surface-to-air missile to intercept a remote-controlled drone as part of Valiant Shield 2016 (VS16). (U.S. Navy photo)
This article is part of the Irregular Warfare Initiative’s Project Maritime, a series exploring the intersection of irregular warfare and the maritime domain. It is republished with permission. Read it in its original form here.
By Walker Mills
The Dnipro River runs more than 1,300 miles, beginning near Smolensk in Russia and emptying into the Black Sea. It is the third-largest river in Europe and is nearly two miles across at its widest points. It cuts across Ukraine for over six hundred miles, from north to south, and bisects several of Ukraine’s largest cities, including the capital, Kyiv.
The importance of river systems in Ukraine highlights the disappointing reality that the United States is neglecting its own riverine capability and, by extension, its ability to control key terrain in future conflicts, even as the US government helps support Ukrainian riverine forces. Competency in riverine warfare will continue to be important in Ukraine whether the conflict continues with high intensity or dampens to a low boil because it can enable high-end combat operations, resistance, or local security operations. Despite clear lessons from Ukraine on the importance of riverine capability, the United States military does not have adequate forces that specialize in riverine or fluvial operations and security. In many military operations, rivers are seen only as obstacles to be crossed, despite the opportunities they present for maneuver and sustainment. However, properly trained and equipped units can use river systems to penetrate behind enemy lines and carry out targeted raids, sustain forces, or secure population centers. Riverine capability is especially important in irregular warfare and asymmetric conflicts because rivers are often key terrain for the military but also support critical infrastructure for civilian populations.
While the US military is equipped to conduct “wet gap” crossings and cross rivers (despite the Marine Corps’s divestment of its bridging companies), it is not adequately prepared to use rivers as a maneuver space—or prevent adversaries from doing the same—and it has not been for years. The US military should maintain a dedicated riverine capability in its conventional forces that can be employed in irregular warfare and beyond, and that can be exported to allies and partners in need. The Army and the Marine Corps have largely abandoned their own riverine capability, and the Navy has precious little left. The Navy’s special boat teams are capable, but only one of the three teams, Special Boat Team 22, is focused on riverine operations and operates a riverine-specific platform, the Special Operations Craft–Riverine (SOC-R). On the conventional side, the Navy’s Maritime Expeditionary Security Forces are chronically underresourced and focused on coastal rather than riverine environments. In a rare bit of good news for riverine capability, Marine Forces Reserve has been moving toward reestablishing a small craft capability for the Marine Corps, though it remains to be seen if the effort will be successful.
Ignoring Our History
Historically, the US military has assembled riverine units in an ad hoc manner when they were needed—usually for counterinsurgency operations. The US Navy, in particular, has a “long and varied but episodic history of riverine operations,” according to a Center for Naval Analyses report. The Army and Navy both have experience in riverine warfare dating back to the American Revolution and inherited experience from even earlier colonial conflicts along North American inland waterways. In the years before and after World War II, the US Navy had a dedicated “Yangtze Patrol” of riverine gunboats conducting security operations in China. Vietnam saw large numbers of soldiers and sailors working to provide security on the Mekong River and elsewhere in the country as part of the Mobile Riverine Force, which was inactivated in 1969. After the invasion of Iraq, Marines in a special riverine company were tasked with providing security for critical infrastructure along the Tigris and Euphrates Rivers, responsibilities that were later taken up by the Navy’s new (at the time) Coastal Riverine Force, which executed thousands of missions and helped train Iraqi police when the Marine unit was disbanded in order to free up personnel for other units. Around the same time an Army unit found the need for riverine capability so critical that it used local fishing boats to patrol Iraqi waterways. But today, there is almost nothing. The Navy has recently rebranded the Coastal Riverine Force as Maritime Expeditionary Security Forces because “riverine warfare is no longer an assigned mission area for the United States Navy, and the legacy name no longer captures the roles and missions of our force.” The change was also part of a shift from irregular warfare to great power competition.
Paradoxically, some of the best American riverine expertise is at the Naval Small Craft Instruction and Technical Training School (NAVSCIATTS), under United States Special Operations Command, but the school only instructs international students from allied and partner nations. NAVSCIATTS is a critical organization that helps the United States export riverine expertise to partners around the world where coastal and riverine forces are not only key to defense, but also to internal security and stability. The Pentagon recognizes that riverine expertise is important enough that we pay to bring hundreds of foreign students per year to the United States to learn it and related skills, but the US military doesn’t maintain adequate riverine capability itself. Worse, NAVSCIATTS is at risk of closure, a move that would also rob many US allies and partners of a key riverine training resource and further gut the US military of resident expertise in riverine operations.
Rivers Aren’t Going Away: The Joint Force Needs More Riverine Capability
The Pentagon needs dedicated riverine warfare capability focused on irregular warfare, but also valuable in other types of operations and in other contexts. Recent US wars have shown the enduring value of brown-water navies in irregular warfare in Iraq and Vietnam and Ukraine is continuing to demonstrate the value of riverine capability in high-intensity conflict. And exporting riverine expertise to allies and partners through training exercises with conventional US riverine forces and schools like NAVSCIATTS is valuable for all of the above.
Exporting US riverine expertise to allies and partners improves American relationships and interoperability. Colombia is one of the best examples of a country that has benefitted from US expertise in riverine warfare, and from US investments in Colombian equipment and training, to the level where Colombia is now a world leader in such operations. Rivers are critical in Colombia because the country relies on over 7,000 miles of navigable rivers for everything from transportation to border security and hydroelectric power. The Colombian military has sent dozens, if not hundreds, of sailors, soldiers, and marines to NAVSCIATTS as students, which has helped transform the Colombian Marine Corps into one of the most capable riverine warfare organizations in the world. Today, the Colombian Marine Corps boasts thirteen riverine battalions supported by indigenously designed and built riverine gunboats and naval aviation—units that were critical in beating back the FARC insurgency and forcing the group to the negotiating table in 2016. Much of Colombia is only accessible by river, and the Colombian Navy and Marine Corps are not just guarantors of security, but the only presence of the state in remote communities where they also help provide basic services like health care. Today, Colombia actually exports riverine expertisefrom its Centro Internacional de Excelencia Avanzada Fluvial (International Center of Advanced Riverine Excellence) to other countries from inside and outside the region, including Costa Rica, Ecuador, and Mozambique, and has designed a family of purpose-built riverine patrol vessels built by COTECMAR, a domestic shipbuilder.
Riverine environments present a dichotomy. On the one hand, recent research from Stanford University shows that navigable rivers historically played a large role in the foundations of economic and political development and are linked with prosperity and democracy. However, riverine environments are also more likely to suffer from insecurity than other environments as they “are susceptible to the greatest shock in security terms.” They are often adjacent to population centers and supply irrigation systems, drinking water, and power generation. Compounding the risk of insecurity, they are also vulnerable to severe weather events, including flooding and drought—both of which are projected to increase due to climate change.
From the Seminole Wars to Vietnam and Iraq, American riverine capability has been critical for irregular warfare and beyond, but assembling the brown-water navy has always been an ad hoc process. The ongoing conflict in Ukraine has demonstrated how important rivers and the riverine environment are to larger, more conventional conflicts in today’s era, characterized by strategic competition as well as irregular conflict. Recognizing this, the US government has announced multiple transfers of dozens of riverine patrol boats, including some likely from its own stocks—a move that ironically emphasizes both the importance of riverine capability and simultaneously, the US military’s disinterest in it. Unlike DoD’s donations of HIMARS, Javelins, and other weaponry, the patrol boats will not be replaced. The US military cannot again wait until riverine capability is in high demand before bringing it back; it needs to establish an enduring conventional riverine capability that can support irregular operations or a large-scale conventional conflict, and everything in between.
Walker D. Mills is a Marine Corps infantry officer and nonresident fellow at Marine Corps University’s Brute Krulak Center for Innovation and Future War and a nonresident fellow with the Irregular Warfare Initiative. The views expressed are those of the author and do not reflect the official position of the United States Military Academy, Department of the Army, or Department of Defense.
Featured Image: JOHN C. STENNIS SPACE CENTER, Mississippi (April 29, 2019) Naval Small Craft Instruction and Technical Training School (NAVSCIATTS) students participate in a Patrol Craft Officer Riverine (PCOR) training exercise on John C. Stennis Space Center, Mississippi, April 29, 2019. (U.S. Navy photos by Michael Williams/RELEASED)
Read Part 1 on defining distributed maritime operations.
By Dmitry Filipoff
As navies look to evolve during the missile age, much of their ability to threaten other fleets will come down to how well they can mass missile firepower. The ability to combine fires against warships heavily depends upon the traits of the weapons themselves. These traits offer a valuable framework for defining the aggregation potential of individual weapons and the broader force’s ability to mass fires.
In the following breakdowns of tactical dynamics and weapon capabilities, it should become clear that virtually all of the U.S. military’s current anti-ship missiles are lacking crucial traits that are essential for massing fires. The consequence is a force with few good options for sinking ships with missiles, and how this could remain the case through the next decade. But new game-changing weapons are on the way, and DMO is the concept that is poised to harness a major transformation in the U.S. Navy’s firepower.
How Mass Fires Define Limits of Distribution
There is a fundamental tension in looking to spread forces out yet still combine their firepower. The range of weaponry is a critical factor that limits the extent to which forces can distribute from another while still being able to combine their fires. This core tension between distribution and aggregation has a strong influence over the tactics and dispositions of a distributed force.
Longer-ranged weapons allow for the broader distribution of launch platforms, while shorter-ranged weapons will force greater concentration. This dynamic can be illustrated using range rings that show the area forces must reside within if they are to combine their fires against a shared target. Range rings are typically used to show the range of a weapon and are centered on the weapon’s launch platform. In this different method of using “reverse” range rings (for lack of a better term), the ring is centered on the target, and shows the area from where the target can be hit by a given weapon. In other words, to strike a target within the range of the Tomahawk missile, a launch platform must be within a 1,000-mile ring of the target.1 Other platforms using the same weapon must also be within this ringed area, highlighting the extent of distribution that is possible while still combining fires. By comparison, platforms using SM-6 or Harpoon have to distribute within much tighter spaces to combine fires (Figure 1).
Launch platforms using different weapons with different ranges must have the rings overlap with one another, at least by the time their fires are combining over the target. These reverse range rings show how longer-range weapons allow for the broader distribution of launch platforms, and how shorter-range weapons, especially versions of the common Harpoon missile, force much tighter concentration around a target (Figure 2).
The specific ranges of missiles are strongly affected by their flight profiles and are not always a linear, set amount in practice. Missiles and aircraft that fly higher earn longer range, partly through the thinner air at higher altitudes.2 But this comes at the expense of being more detectable and potentially less survivable. Low altitude sea-skimming flight maximizes the element of surprise at a significant cost to range and fuel economy. Different flight profiles can be programmed into missiles depending on the tactical circumstances, and many anti-ship missiles can be programmed with non-linear flight paths and waypoints.3 It is often unclear in publicly available information what kind of flight profile is associated with the published range of the missile.
These factors make range rings more elastic than they appear. This variability of flight profiles adds another dimension of complexity to combining fires. For the sake of consistency in the graphics used here, it is assumed that all missiles of the same type are using the same flight profile in linear attacks. Another elastic factor is the maximum effective range of a weapon, which is not the same as the maximum flying range. The distance a missile can be effectively targeted can be less than how far the missile can travel. Maximum flying ranges are used here for consistency.
Having long-range weaponry is extremely valuable in modern naval warfare because weapon range helps shifts the burden of maneuver from the slower platform to the faster payload. This advantage is especially critical to navies because of the significant speed differential between ships and missiles. A warship with a short-ranged anti-ship missile would have to maneuver for hours and even days to strike multiple targets spread across an ocean. But a warship with a long-ranged weapon could hold all those same targets at risk simultaneously with no maneuver. A single warship with Tomahawk can hold targets near Luzon, Taiwan, and Okinawa at risk simultaneously, while a ship with SM-6 could only hold one of those areas at risk at a time. The warship with SM-6 would have to spend significant time maneuvering to eventually hold all of these areas at risk, and only in sequence (Figure 3).
This relationship between range and maneuver highlights the critical dynamic of how one force’s distribution can make the adversary’s stretched thin or concentrated. If one force package has shorter-ranged weapons than its adversary, it has less space it can distribute within and still combine fires. The short-ranged force package is more concentrated than its opposition, and may only be able to threaten one portion of the opposing distributed force at a time, if it can get in range. By comparison, many more elements of the distributed force can hold the shorter-ranged force at risk, and from safer standoff distances. Rings within rings can illustrate how the force with longer-ranged weapons can enjoy a broader distribution and mass firing advantage over a force with less range (Figures 4 and 5).
What can be defined as distributed, concentrated, or stretched thin is less a matter of a specific range or density of forces. Rather, it is better understood as a relationship between one’s own capabilities, and how that compares to the relationship between the capabilities of the adversary. A force that believes it is well-distributed could actually be heavily concentrated in the context of an adversary with much longer-ranged capability.
Anti-ship weapons that are specifically designed for multi-role aircraft are often much smaller than warship-based weapons that are fielded in large launch cells, which often causes these aircraft-based weapons to have lesser range. Aircraft can compensate for lesser weapons range with their faster platform maneuver, whereas warships can compensate for their slower platform maneuver with the longer range of their larger weapons. Understanding this relationship between platform maneuver and payload maneuver and how they can complement and compensate for one another is critical to assembling massed fires.
But range is only one critical variable for assessing the ability to mass fires. Other critical traits include launch cell compatibility, platform compatibility, number of weapons procured, and numbers of weapons fielded per platform. These traits combine to highlight the true extent of a navy’s offensive firepower.
Harpoon and the Perils of Carrier Strike
The Harpoon missile was the U.S. Navy’s first anti-ship missile and has remained its primary anti-ship weapon for more than 45 years.4 The way the U.S. Navy has continued to field this missile has created severe operational liabilities for U.S. sea control and the credibility of American security guarantees in the Indo-Pacific writ large. The Harpoon missile underscores a critical capability gap of major strategic significance by highlighting just how little anti-ship missile firepower the U.S. military has. The weapon’s shortcomings are emphasized by the especially risky tactics the U.S. would be forced to use in war to make much use of it.
The Harpoon missile’s greatest weakness comes through its combination of short range at 80 miles for the more common variants and the lack of meaningful inventory in all its compatible launch platforms save for one – aircraft carriers.5 The short range of this missile draws the U.S. Navy’s most expensive and least risk-worthy platform deeper into the battlespace, while funneling carrier air wings into exceedingly concentrated anti-ship attacks. But because the U.S. Navy has lagged for decades in fielding a meaningful replacement for Harpoon, the highly risky method of attacking ships with carrier air wings is the only tactic the U.S. military effectively has for sinking high-end warships at long range.
The Harpoon missile has the broadest platform compatibility of any U.S. anti-ship weapon, where it can be fielded by submarines, surface ships, bombers, land-based launchers (which the U.S. sells to partners but does not procure for itself), and carrier air wings. But despite the U.S. Navy having more than 9,000 vertical launch cells for missiles, the Harpoon is incompatible with these launchers.6 Instead, it has to be kept in torpedo racks or in launchers mounted topside, which are highly uneconomical methods that severely reduce the number of weapons that can be fielded per warship. U.S. Navy destroyers and cruisers only carry eight Harpoon missiles despite having around 100 launch cells per platform, and the number of torpedo tubes per submarine typically numbers in the single digits. What launch cells offer is significant magazine depth on both an individual platform and force-wide basis, making launch cell compatibility a crucial trait for massing fires.
As a general rule of thumb, any alert and modern warship larger than a corvette should be able to hold its own against a salvo of only eight subsonic anti-ship missiles, or else the warship can hardly justify its cost. U.S. surface and submarine launch platforms are hardly able to muster enough volume of fire to credibly threaten most modern warships with their sparse inventories of Harpoon missiles. This shallow magazine depth creates a strong need for massing fires between multiple platforms to achieve enough volume of fire. But the extremely short range of Harpoon means this weapon has barely any potential for aggregation with other ship-launched Harpoon missiles, unless commanders are willing to concentrate numerous warships to an extreme degree.
This combination of launch cell incompatibility and short range in the Navy’s mainstay anti-ship weapon forces carrier aviation to shoulder most of the burden of massing enough volume of fire. Only the air wing can conceivably mass enough platforms to create enough volume of fire, while having a chance of getting those platforms close enough to a target warship to launch a strike. These factors make aircraft carriers the only platform that can muster a combat credible volume of Harpoon fire.
An F/A-18 Hornet can equip up to four Harpoon missiles, where only two of these aircraft can match the Harpoon firepower of a U.S. Navy cruiser or destroyer. But against high-end warships, achieving combat credible volumes of Harpoon fire requires massing large numbers of carrier aircraft. Overwhelming a single surface action group of several modern destroyers, each with dozens of anti-air weapons and several layers of hardkill and softkill defenses, could conceivably require the majority of an air wing. The remaining few aircraft would be thinly stretched between maintaining combat air patrols, providing tanking and jamming support to the striking squadrons, among other roles. By heavily concentrating the burden of massing volume of fire on air wings, those air wings are subsequently stretched thin across a multitude of other critical missions.
Attempting to mass fires with a missile that is very short-ranged creates severe tactical risks. The short range of Harpoon forces an extremely tight and dense concentration of carrier aircraft around the target to muster enough firepower to be overwhelming. Harpoon’s short range also makes it a weapon that cannot always be confidently fired from standoff distances beyond the range of modern air defenses, unlike many anti-ship missiles. Instead, Harpoon can force air wings to concentrate themselves well within the range of opposing shipboard air defenses. Warship air defense weapons, such as China’s HHQ-9B missiles, can approach and even exceed the short ranges of the Harpoon, putting adversaries into the more favorable position of being able to threaten archers before they can fire arrows (Figure 6).7
Survivability concerns not only apply to carriers, but to their air wings as well. Air wings are highly sensitive to attrition, where losing even a few aircraft per sortie can quickly render certain missions unsustainable. This is especially true for anti-ship missions that require large numbers of aircraft to achieve sufficient volume of fire. The Navy’s air wings can be risking substantial losses by using a missile that is so short ranged that it can force them to send large and tightly concentrated aerial formations into the teeth of modern naval air defenses. The air wing’s ability to mass enough anti-ship firepower would be rendered impotent in a matter of days if not hours by suffering even minor losses on only a few of these risky strikes.
Carrier air wings may be resisted by far more than warship air defenses. The signature posed by a mass of carrier aircraft heading toward a target at high altitude could provide plenty of warning to vector opposing airpower into position to blunt the strike. Compared to the aircraft defending the airspace, anti-ship squadrons would likely be at a hardpoint and maneuverability disadvantage. Many of their hardpoints would be taken up by a combination of heavy anti-ship weapons and drop tanks, with potentially fewer anti-air weapons loaded compared to the opposing dogfighters. If the anti-ship aircraft are intercepted before they are within range of attacking warships, they may be forced to dogfight and evade missiles while having their maneuverability impacted by the heavy anti-ship weapon loadouts. Drop tanks, anti-air, and anti-ship weapons will compete for similar hardpoints on carrier aircraft, setting the stage for difficult tradeoffs between survivability, concentration, and mustering enough volume of cruise missile fires.
Anti-ship strikes can be conducted near the limits of the air wing’s range to maximize standoff distance. But the short range of Harpoon combined with the relatively short range of current generation carrier aircraft (compared to past and future generations of air wings), forces the carrier deeper into the contested battlespace and potentially incurs more risk. Harpoon not only threatens the tight concentration of valuable carrier aircraft around targets, it threatens to pull the carrier itself deeper into riskier territory.
Extending the range of the air wing through drop tanks or tanking aircraft can help keep the carrier further out, but this will diminish the volume of firepower by devoting hardpoints and aircraft to fuel instead of weapons. This can benefit the survivability of the carriers more than the air wings, where adding range to the air wing can improve the carrier’s survivability by allowing it to launch strikes from further away. But this will do less for the air wing’s survivability because the short range of their anti-ship weapons will still force tight concentration around the target regardless.
When it comes to managing the signatures of aircraft carriers, not only does the signature of the carrier have to be taken into account, but the signature of the air wing as well. The signatures and footprints of air wing operations can contribute toward concealing or revealing the carrier’s location. Maximizing the standoff range of an air wing launching a massed anti-ship strike encourages a more linear flight path to and from the target, a denser concentration of aircraft throughout the flight path, and higher altitude flight that extends the range but increases the detectability of the aircraft. Even though it maximizes standoff distance, a linear flight path could more easily lead an adversary back to the carrier by virtue of predictability.
Shortening the carrier’s range to the target or devoting more hardpoints and aircraft to fueling can give the air wing more margin to increase the complexity of force presentation. It can allow the air wing to more widely distribute itself and take nonlinear paths to and from the target, which can help conceal the carrier’s location (Figure 7). However, ensuring a disaggregated air wing can effectively come together on time to mass fires poses more complex challenges for mission planning compared to a more linear strike, especially when combining fires with other types of platforms. And a distributed nonlinear flight profile may have to come at the cost of decreasing the overall striking range of the carrier and pull it deeper into the battlespace.
Overall, many of the survivability concerns and tradeoffs of using air wings and carriers in anti-ship roles are substantially worsened by the Harpoon missile’s traits. But the major advantage Harpoon has over all the other anti-ship weapons in the U.S. arsenal is its inventory numbers. While recent public information on current figures appears unavailable, data from the 1990s suggests an inventory of as many as 6,000 missiles.8 It is reasonable to assume that the figure today remains in the thousands, compared to most other U.S. anti-ship missiles which have been procured only in the hundreds or dozens. But the ability to leverage the depth of the Harpoon inventory is tightly bottlenecked by the shallowness of the individual platform magazines it is fielded in, given its launch cell incompatibility.
Due to the major risks air wings and carriers must take to effectively mass the very short-ranged Harpoon, maybe the Navy’s carriers would be better served by not using this weapon in a fleet-on-fleet fight. Doing so could enhance the survivability of carriers, air wings, and the surface ships that escort them. But it would mean coming to terms with how the vast majority of the U.S. Navy’s force structure and missile arsenal is hardly able to threaten modern naval formations with anti-ship firepower. Virtually all of the U.S. military’s anti-ship capability could then be narrowly confined to what the submarine force can accomplish with torpedoes alone.
One has to be careful about extrapolating specific tactics from basic weapon limits, given how shortcomings in capability can be compensated by creative operational design. Maybe the Navy is counting on the submarine force sinking the adversary’s high-end surface combatants to pave the way for carrier anti-ship strikes, but that will do little against the land-based airpower those carrier aircraft may still have to tangle with.
This design of having the entirety of the U.S. military’s long-range anti-ship capability completely concentrated in massive aircraft carriers, who must in turn heavily concentrate their valuable air wings to execute the tactic, is extremely contrary to the principle of distribution. What Harpoon tactics reveal is that after severely lagging in anti-ship missile development for more than half a century, the U.S. Navy has deprived itself of many critical options for fighting another great power navy.
SM-6 and Diluting Capability Across Missions
The SM-6 is unique among the Navy’s anti-ship missiles. It is the only supersonic anti-ship weapon in the Navy’s arsenal, it can be used against both aerial and warship targets, and it has the highest production rate of the Navy’s latest generation of anti-ship weapons. Featuring 150 miles of range for the more common variants, it offers a modest improvement of range over the latest Harpoon variants.9 It is also the only Navy shipboard anti-air missile that may be used to aggregate defensive firepower at long range. However, some of the supposed strengths of SM-6 create drawbacks when it comes to massing firepower for anti-ship strikes.
The high speed of the SM-6, which is more than Mach 3, improves the survivability and lethality of the missile when it comes to breaking through warship defenses and striking the target at high speeds.10 However, the high speed of the missile complicates its ability to combine fires with the Navy’s other anti-ship weapons, which are all subsonic. If SM-6 is to combine with subsonic missiles, then it must either be fired near the end of a mass firing sequence to ensure timely overlap, or the platforms firing subsonic missiles must be much closer to the target than the warship firing SM-6. (This dynamic will be discussed more closely in Part 3.)
The multi-mission versatility of the weapon poses challenges for effective mass fires by complicating release authorities. If a distributed force is to combine anti-ship fires across multiple platforms, then the release authority for offensive anti-ship weapons may naturally reside at a higher echelon than the commander of an individual ship, who typically lacks the organic sensors to target these weapons against warships at long range. But the intense speed and lethality of missile attacks on warships means individual commanders should be afforded the authority to prosecute their local air defense missions with great initiative, especially to avoid defeat in detail. If a unit-level commander feels compelled to employ SM-6 for the sake of ship self-defense, then that may diminish a higher-echelon commander’s options for massing anti-ship fires.
The typical flight profile of long-range anti-air weapons poses another challenge to the effectiveness of SM-6 as an anti-ship weapon. While long-range anti-air weapons can certainly hit sea-level targets, their initial phase of flight typically involves a boost phase that takes them to higher altitude.11 Higher altitude makes it easier for the missile to achieve its maximum speed and range before it descends back down to hit lower-altitude threats. However, a higher altitude flight profile creates disadvantages when attacking warships. High-altitude flight broadens the area from which a missile can be detected and engaged from, possibly giving more warships the opportunity to engage the missile and with more time to take multiple shots. Sea-skimming flight by comparison can force air defense engagements into the immediate area of only the target warship. The SM-6 missile’s high speed is not so great that it effectively compensates for these risks of high-altitude flight. The boost phase of an SM-6 launch can give almost double the reaction time to a target warship’s radars compared to a slower subsonic missile that is only detected after it breaks over the target’s horizon.12
It is unclear if SM-6 can be fired on a flatter trajectory and maintain an end-to-end sea-skimming flight profile. Doing so would likely deprive it of a significant amount of range. It would also make it more difficult for the missile to apply the greatest source of its lethality against warships – its high speed. The warheads of anti-air weapons are much smaller than those of purpose-built anti-ship weapons, where the warhead of SM-6 is about only 15 percent of the size of an LRASM or Tomahawk warhead.13 SM-6 needs to reach high speeds to be at its most lethal against warships, but achieving those speeds is heavily dependent on higher-altitude flight profiles that make the missile less survivable.
The range of SM-6 is not so long that its offensive anti-ship roles can be cleanly separated from its defensive anti-air roles. The concept of “standoff” fires implies that a valuable margin of survivability can be earned by outranging an opponent’s ability to strike back. But the range of many great power anti-ship missiles is great enough to where SM-6 cannot be comfortably used in a purely standoff role for attacking modern warships. If a warship is within range of attacking another high-end warship with SM-6, then it is also likely within range of anti-ship missile threats that could force the ship to expend SM-6 on defense instead. This effect becomes even more relevant when longer-ranged weapons like opposing anti-ship ballistic missiles can cast a long shadow over thousands of miles of ocean.14 Commanders may opt to reserve their most capable air defense weapon for protection against the adversary’s most capable anti-ship missiles.
Because modern anti-ship weapons tend to outrange most anti-air weapons, it is much more feasible to combine offensive firepower than defensive firepower from across distributed forces. SM-6 may mark an exception by using the unique NIFC-CA capability that allows it to be targeted beneath the radar horizon of the launching warship. The range of SM-6, its high speed relative to the subsonic anti-ship missiles it could be used against, and its ability to be retargeted beneath the horizon make the aggregation of defensive firepower possible.15 This is an especially unique capability, but adds more complexity to the command-and-control arrangements undergirding massed fires.
Compared to all of the Navy’s other modern anti-ship missiles (excluding the aging Harpoon), SM-6 has an advantage in being produced at consistent full-rate production for a number of years since being introduced in 2013, with more than 1,300 missiles in the inventory.16 By comparison, all of the Navy’s other latest generation of anti-ship weapons currently exist in very low numbers that make them hardly applicable to the large-scale salvo requirements of modern naval warfare.
However, most of the SM-6 production runs to date have been for earlier variants whose anti-ship ranges are only marginally better than the latest Harpoon variants.17 While longer-ranged versions of SM-6 are forthcoming, the vast majority of the current inventory will offer little improvement in broadening the extent to which warships can distribute and still be able to combine fires.
Even if longer-ranged versions of SM-6 quickly arrive in large numbers, much of the missile’s versatility could have to be set aside to fill the Navy’s critical anti-ship capability gap through the near term. SM-6 is currently the Navy’s only somewhat numerous, launch-cell compatible, and long-range anti-ship weapon. But its multi-mission capabilities threaten to dilute the inventory across diverse threats. The Navy may be forced to maintain SM-6 as its only viable modern anti-ship missile until other anti-ship weapons are produced in large enough numbers to make a real difference and free SM-6 to fulfill its air defense potential. But given how current production runs are trending, this could take at least 10-15 years to accomplish. If the Navy finds itself in a major naval conflict this decade, it may be forced to forego much of SM-6’s cutting edge air defense capability for the sake of retaining a modicum of long-range anti-ship firepower.
Maritime Strike Tomahawk – The Foundational Enabler of Massed Fires
More than 40 years after an anti-ship Tomahawk first struck a seaborne target in testing, the Navy will be reintroducing an anti-ship variant of the missile.18 More so than any other U.S. anti-ship weapon to be fielded in the coming years, the Maritime Strike Tomahawk holds the greatest promise in fostering a major evolution in the Navy’s ability to distribute platforms and mass anti-ship fires.
Tomahawk’s great advantage is its combination of launch cell compatibility and very long range at more than 1,000 miles.19 Many platforms will be able to carry large numbers of an especially long-range weapon, creating a wide range of options for massing fires. Long range also gives the weapon more opportunity to vary its flight paths and use waypointing, which can be used to execute a variety of tactics and facilitate aggregation with other salvos.
By finally having an anti-ship missile that is both long-range and launch cell compatible, the Navy will be poised to drastically increase the amount of anti-ship firepower across a much greater distribution of platforms. Land-based Tomahawk launchers are also on the way for the U.S. Army and Marine Corps, which will significantly increase options for massing fires if those services procure the weapon in major numbers.20
However, the Maritime Strike Tomahawk’s potential will not be fully realized until many years from now. It will not reach initial operating capability until 2024 and is currently in its early years of low-rate initial production and testing, with roughly 100 MST kits procured so far.21 The Navy is looking to upgrade all of its Block IV Tomahawks into Block V variants, and it is possible up to 300 recertification kits may be installed per year.22 But it is unclear if every recertification will also add the maritime strike capability through the specific Block Va configuration.23
At this rate, it could take 10 or more years before the Navy has enough inventory of the foundational missile that will allow it to truly make distributed and massed anti-ship fires a reality.
LRASM – A Leap Forward Yet Still More of the Same
The Long-Range Anti-Ship Missile (LRASM) will mark an important upgrade to the Navy’s anti-ship firepower. Featuring a stealthy profile and an estimated range of around 350 miles, LRASM outranges all of the Navy’s other anti-ship weapons except for Tomahawk.24 Yet LRASM does little to enhance the Navy’s ability to mass fires from across distributed forces.
LRASM’s potential for mass fires is heavily constrained by platform compatibility because it is not a launch cell compatible weapon. LRASM can only currently be fielded by bombers and carrier aircraft. Despite tests suggesting that LRASM can be fired from launch cells, the Navy continues to describe the program as “a key air launched component of the Navy’s overall Cruise Missile Strategy…”25 In 2021, industry partnered with an Australian firm to refine the development of a surface-launched variant of LRASM that has been termed “LRASM SL,” suggesting that launch cell compatible versions of this weapon are distinct from what the U.S. Navy is procuring for itself.26
Even though LRASM’s range makes it a much less risky missile for air wings to fire at targets compared to Harpoon, these strikes would still tie down a large portion of the air wing to mass enough firepower to be overwhelming. LRASM does not alleviate the need for large volume of fire, which strains the air wing’s ability to cover multiple other roles besides strike. Even with its advanced capabilities, LRASM will not change certain fundamental disadvantages of massing air wings to conduct long-range strikes against warships.
The amount of LRASM inventory is extremely low at about 250 missiles procured for the Navy so far.27 The Air Force’s inventory is even smaller and only numbers slightly less than 100.28 Although the Air Force’s bombers can equip Harpoon missiles, the short range of that weapon and their especially low procurement rate of LRASM may mean the U.S. military’s bombers will have barely any anti-ship firepower to contribute to U.S. sea control for the foreseeable future.
LRASM shares a production line with the much more numerous Joint Air-to-Surface Standoff Missile (JASSM) it is adapted from, and where more than 2,000 JASSM weapons have been procured by the U.S. Air Force so far, and where the Navy has begun to procure the weapon within the past two years.29 The newest forthcoming “extreme range” variants of the JASSM ground-attack missile will feature ranges of up to 1,000 miles, making it one of the first air-launched cruise missiles that can rival the ranges of Tomahawk.30 The JASSM production line is also the most robust of any of the missiles described thus far, with annual production runs numbering in the hundreds as opposed to the other missiles that are only being procured by the dozens.31
The two anti-ship weapons that hold the most promise, LRASM and Maritime Strike Tomahawk, are adaptations of existing munitions that have been produced in far greater numbers – JASSM and the land-attack Tomahawk. Upgrading these existing weapons with anti-ship capabilities and seekers may be a more rapid and cost-effective way to ramp up the anti-ship weapon inventory of the U.S. military compared to building new weapons wholesale. If the forthcoming extended-range variants of JASSM can feature anti-ship capabilities, then the U.S. military will open up a vast array of new options for the distribution and aggregation of firepower between naval and air forces.
Naval Strike Missile – Only Slightly Better Than Harpoon
The Naval Strike Missile (NSM) features a stealthy profile and an advanced seeker, but it brings only a marginal improvement over Harpoon. Similar to Harpoon, NSM has relatively short range at 115 miles and it is not compatible with launch cells.32 It is mainly being fielded by the Navy’s Littoral Combat Ships with only eight weapons per ship, and the Marines are procuring a land-based version. Its short range and launch cell incompatibility make this weapon poorly suited for massing fires from distributed forces. Low procurement rates put the current inventory at slightly more than 110 missiles, hardly enough to make the weapon widely fielded and available for mass fires.33 The main utility of both Harpoon and NSM in a major naval conflict may be relegated to engagements against smaller and more isolated combatants, perhaps in secondary theaters and areas peripheral to larger salvo exchanges.
A Brittle Spear
The ability to mass fires is fundamentally enabled by fielding a large number of long-range missiles across a wide variety of platforms. In terms of numbers, range, and variety, the U.S. military falls woefully short. The U.S. military cannot execute the tactic of distributed massed fires against warships today because it simply does not have the weapons to make it possible. Its current anti-ship missile firepower is extremely concentrated in aircraft carriers and tightly stretched thin everywhere else.
None of the newer U.S. anti-ship missiles will do much to improve the Navy’s ability to distribute and still combine fires, except for Tomahawk. LRASM can somewhat broaden the scope of physical distribution of launch platforms, but it is still a heavily concentrating weapon due to its narrow platform compatibility. LRASM will do little to alleviate the carrier’s heavy burden of shouldering most of the U.S. Navy’s anti-ship capability.
The Maritime Strike Tomahawk strongly stands out as the weapon with the most transformational promise, and it is absolutely fundamental to manifesting DMO. Finally the U.S. Navy will have anti-ship weaponry that is both long-range and compatible with its launch cells, and finally the U.S. military will have more viable anti-ship missile platforms than just carriers. This stands in sharp contrast to great power competitors, who have already broadly distributed anti-ship firepower across their surface fleets, bombers, land-based forces, and submarines.34
A central risk factor is considering what proportion of the overall volume of fire each type of weapon may contribute. Based on these key traits, more risk is incurred the less suitable a weapon is for mass fires. Weapons such as Harpoon or the Naval Strike Missile can certainly add a fraction of the contributing fires, but the more these weapons make up mass fires, the more risk the force will have to assume.
Among the weapon traits analyzed, the depth of inventory stands out as an especially critical constraint in the capital-intensive nature of modern naval salvo combat. Even if highly capable missiles are being procured, inventory depth is the key variable that will prevent the U.S. military from having enough modern anti-ship missile firepower through at least the rest of this decade. Current stocks of modern U.S. anti-ship missiles are not remotely close to satisfying the demands of a type of combat that can require more than a hundred missiles to overwhelm the defenses of only a few destroyers, where a decade’s worth of weapons procurement can easily be discharged in a matter of hours.
As it currently stands, most of the inventory of the Navy’s anti-ship missiles except for Harpoon could be spent in a handful of salvo engagements. The appropriate amount to meet great power naval threats is not dozens or even hundreds of weapons, but thousands – a figure that grossly exceeds the inventory of all of the U.S. military’s latest generation of anti-ship weapons. And even if procurement rates have substantially grown the inventory 15 years from now, competitors could have grown their own arsenals over the same period, such as by building out deep inventories of anti-ship ballistic missiles and hypersonics that sustain a critical margin of overmatch.
It is unclear how exactly the U.S. military has chosen to distribute or concentrate its small but growing inventory of modern anti-ship weapons. A major crisis could force the U.S. military to scrounge across the force in a rush to assemble enough weapons to field an adequate volume of fire. If these rare weapons are spread across the east- and west coast-based fleets, the Navy may be forced to engage in an elaborate act of transcontinental crossdecking to concentrate enough credible firepower in crisis response units.
These pervasive capability gaps have created a major window of opportunity for great power challengers to capitalize on the strategic liability posed by the weakness of the American naval arsenal. Until new weapons are fielded in large enough numbers, the U.S. military may be forced to endanger its single most expensive platform to close the gap – aircraft carriers.
Part 3 will focus on assembling massed fires and modern fleet tactics.
7. J. Michael Dahm, “A Survey of Technologies and Capabilities on China’s Military Outposts in the South China Sea,” South China Sea Military Capability Series, Johns Hopkins Applied Physics Laboratory, pg. 6, March 2021, https://apps.dtic.mil/sti/pdfs/AD1128637.pdf.
12. This calculation was arrived at by dividing the range of the SM-6 (150 miles) using the SM-6’s Mach 3.5 speed (2,685 miles), adding about 30 seconds to account for acceleration to max speed from launch, and a radar horizon profile of a radar mounted 30ft. high and the SM-6 coming into view at about 7,000 feet of altitude, which corresponds to the 150 mile range of the weapon. This comes to about four minutes of warning to the target warship. The subsonic missile time is calculated at 550mph breaking over a horizon that is 20 miles, giving the target warship slightly more than two minutes of warning.
18. For 1982 test date: E. H. Corirow, G. K. Smith, A. A. Barboux, “The Joint Cruise Missiles Project: An Acquisition History, Appendixes,” RAND, pg. 46, August 1982, https://www.rand.org/pubs/notes/N1989.html.
Statement of Frederick J. Stefany, Principal Civilian Deputy, Assistant Secretary of the Navy (Research, Development and Acquisition), Performing the Duties of the Assistant Secretary of the Navy (Research, Development and Acquisition) and Vice Admiral Scott Conn, Deputy Chief of Naval Operations, Warfighting Requirements and Capabilities (OPNAV N9) and Lieutenant General Karsten S. Heckl, Deputy Commandant, Combat Development and Integration, Commanding General, Marine Corps Combat Development Command, before the Subcommittee on Seapower of the Senate Armed Services Committee on Department of the Navy Fiscal Year 2023 Budget Request for Seapower, PDF pages 31-32, April 26, 2022, https://www.armed-services.senate.gov/imo/media/doc/HS_26APR22_RDA_SASC_S_DON_PB23_Shipbuilding_Aviation_Ground_FINAL%20(2).PDF.
Featured Image: PHILIPPINE SEA (Oct. 1, 2019) Independence-variant littoral combat ship USS Gabrielle Giffords (LCS 10) launches a Naval Strike Missile (NSM) during exercise Pacific Griffin. (U.S. Navy Photo by Mass Communication Specialist 3rd Class Josiah J. Kunkle)