Tag Archives: ASW

Tactics and Warfighting

Make ASW Joint: Integrating the Joint Force into Full Spectrum ASW

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By Jason Lancaster

Winston Churchill once stated that the only thing that scared him during the Second World War was the subsea aspect during the Battle of the Atlantic. Ant-submarine Warfare (ASW) was a paramount focus early in the war. Victory in the Atlantic required a whole of government effort from the Allied powers at the war’s strategic, operational, and tactical levels. At the strategic level, national shipbuilding industries designed ships like the Flower-class corvette and Liberty cargo ship for mass production. At the operational and tactical level, Allied air forces and navies were forced to operate jointly to hunt submarines and defend convoys.

During the Cold War, NATO maintained anti-submarine competency and internalized lessons learned during the Second World War. The collapse of the Soviet Navy during the 1990s shifted the U.S. focus to power projection ashore in the Balkans and the Middle East, and anti-submarine warfare competencies across the joint force atrophied. As the era of near-peer competition began, the Navy looked at ways to recapture the hard-fought competencies and lessons lost since the end of the Cold War. In particular, the whole government approach to anti-submarine warfare (ASW) was reintroduced, known as “full-spectrum ASW.” The Navy is the domain owner for undersea warfare. As such, the Navy must be prepared to educate and explain undersea warfare doctrine and its roles to the rest of the joint force so that lessons written in blood are not repeated.

A Disappointing Tale of Disjointedness

As a young lieutenant serving at Naval Forces in Korea, I received a frantic call from a United States Forces Korea staff officer to come over for a chat. Once there, an Air Force officer asked me how to make anti-submarine warfare a joint activity. Inadvertently, my recommendations aligned with the concepts of “full-spectrum ASW,” first described by retired Navy captain William Toti. During the meeting, I detailed several ways to accomplish anti-submarine warfare as a joint activity. A few hours later, I received a call from an Air Force officer stating that headquarters decided that anti-submarine warfare was a Navy problem, a position reminiscent of the historical friction between the Army Air Corps and the Navy in 1942. History has a way of repeating itself.

Anti-Submarine Warfare (ASW) is All-of-Government and Joint

Full-spectrum ASW breaks down the different ways to defeat a submarine threat. There are offensive and defensive lines of effort or threads. The threads cover the strategic, operational, and tactical levels of war. These threads require an all-of-government approach to recognize their full benefit and potential. Captain Toti was inspired by the Army’s combined arms tactics and use of kill zones to approach anti-submarine warfare. Using my previously mentioned conversation as an inspiration, this paper journeys through the different threads of integrating full-spectrum ASW into the joint force and not leaving it just to the Navy.

Strategic Threads

The joint force contributes variously at the levels of war for full-spectrum ASW. There are only two threads at the strategic level of war. If used aggressively by joint force commanders, those two threads can end a submarine threat before it has begun.

1. Discourage enemy submarines before leaving the harbor. Discouraging enemy submarines from leaving port occurs at senior levels of government and the combatant command through overt and covert means. Commanders and the government should conduct studies to determine enemy submarine force capability gaps to exploit. This should be all-encompassing and explore everything from adversary submarine force leadership, command and control, tactics, training, parts and maintenance, and morale. Discouraging an enemy submarine from leaving port would focus on deterring its leadership, disrupting command and control, and exploiting any issues with submarine force morale. Many of these efforts can be considered part of information operations or operations designed to influence the decision calculus of enemy leadership and crews to create favorable outcomes for the joint forces.

2. Defeat submarines in port. The adage is that the best time to eliminate a submarine is when it’s stationary alongside a pier. In 1982, the ARS Santa Fe was sunk alongside a pier on South Georgia Island by a Royal Navy helicopter. This reduced the Argentine Navy’s submarine fleet by a third before the amphibious landings in the Falklands began. The remaining two Argentine submarines proved troublesome for the Royal Fleet. The Royal Navy expended significant quantities of sonobuoys, torpedoes, aircraft sorties, and ships hunting the other submarines. On several occasions, Argentine torpedo failures proved to be the only thing that prevented successful submarine attacks on Royal Navy ships. Although the Royal Navy never located the other two submarines, their efforts proved it was easier to kill submarines in port than at sea.

Defeating submarines in port is more aggressive and highly escalatory if done during peacetime. However, diplomacy and sanctions can restrict the flow of required parts and supplies, affecting readiness and preventing a submarine’s departure from port. Such strategies are hard to implement for adversaries with strong indigenous supply chains. During wartime, special operation raids and time-sensitive targeting can help disable vessels in port.

Infrastructure strikes on piers, warehouses, fuel storage, ammunition magazines, and communication nodes can hobble sustainment capabilities. An enemy submarine can return to port but cannot be redeployed. Mining the entrances or approaches to harbors can quarantine the threat, at least temporarily. Defeating submarines in port simplifies theater ASW and enables logistics to flow into the theater with less risk.

Russian Navy nuclear-powered submarines at a base in Russia’s Murmansk region. (Photo via Lev Fedoseyev/TASS)

Operational Level of War

Anti-submarine warfare (ASW) is a resource-intensive fight. The time to learn and prepare is before hostilities break out. The combatant commander should support joint operations at the operational level of war by prioritizing and resourcing ASW as a key mission and emphasizing routine training requirements. ASW exercises illuminate the gaps in coverage within the operating area. Once those gaps are identified, the command can submit an urgent needs request to acquire additional capabilities to support the ASW mission. Urgent is relative to the budgeting time frame, so the joint force commander should identify these needs early to build a case for how these capabilities are required in the theater.

3. Defeat the submarines’ shore-based command-and-control (C2) capability. Severing leadership’s communications with their operational units ranges from destroying nodes, jamming channels, hacking command and control systems, and targeting leadership. Submariners embody mission command, but disrupting the command-and-control capability reduces the effectiveness of over-the-horizon targeting. If the enemy submarine does not have third-party sensor cues for the location of our ships, the submarine is forced to approach the strike group for organic acquisition. As a submarine draws closer to a protected entity, its advantages are eroded, and its chance of discovery is elevated. Disrupting communications also adds a layer of distraction, forcing adversarial crews to make efforts to restore communications.

4. Defeat submarines near ports and in denied areas. In the late 1940s and early 1950s, anti-submarine aircraft operated in spotter-killer groups. One carried the sensors, and the other carried the torpedo. Today, General Atomics builds the sensor-laden MQ-9B capable of carrying side-scanning maritime radars and 40 sonobuoys. Another unmanned aerial system, the T600, successfully launched a Stingray torpedo during a NATO exercise. While U.S. maritime patrol aircraft like the P-8A Poseidon are adept submarine hunters, there are too few of them.

British Aerospace’s T600 prepares for takeoff with a torpedo. (Photo via DroneXL)

Hunting submarines is an excellent area where the joint force can shine. The Marine Corps should invest in the MQ-9B to support their Marine littoral regiments’ domain awareness and anti-submarine warfare initiatives. These aircraft could operate from expeditionary advanced bases near a hostile country to detect, track, classify, and engage hostile submarines.

5. Defeat submarines in chokepoints. Chokepoints are dangerous for warring sides depending on who has the preponderance of forces and who can position first. Diesel-electric submarines are slow and cannot easily close on a maneuvering carrier strike group. Instead, diesel-electric submarines prefer to lie in wait. Chokepoints are key maritime terrain to funnel forces and favor ambush predators. This is an area where the Marine Corps littoral regiments and the Army multi-domain task forces can play a decisive role with the proper weapons.

The Marine Corps littoral regiments and multi-domain task forces expect to operate near chokepoints, providing sensors and fires for the maritime fight. Equipping them with weapons and sensors that support anti-surface and submarine warfare would increase their lethality and utility in chokepoints. Equipping these units with MQ-9B Sea Guardians would provide persistent maritime domain awareness for the joint force. The Department of Defense should develop an extended-range dual-use anti-submarine/anti-ship cruise missile for the joint force like the Russian SS-N-14 Silex. These units could rely on inorganic sensors or be equipped with periscope detection radars, sonobuoys, and sonar processing systems to direct their maritime fires.

These units are already equipped with anti-ship missiles such as the SM-6, Block V Tomahawk, and Naval Strike Missile (NSM). Increasing the variety of weapons and capabilities makes these forces more lethal and forces the enemy to develop countermeasures, diverting resources from offensive weapons.

Two towboats attached to a submarine flotilla under the PLA Northern Theater Command jointly tow a submarine off a port during a maritime combat training exercise on April 19, 2022. (Photo via eng.chinamil.com.cn/photo by Shi Jialong)

6. Defeat submarines in the open ocean. There are two key ways that the joint force can support the open ocean ASW fight. One is through providing additional intelligence support. Cryptologic Task Group (CTG) 101 is collocated with the Air Force, Space Force, and other agencies. It provides timely, accurate, and relevant target quality data on dynamic targets to enable weapons engagement at range. If the next fight is maritime, CTG 101 mission priorities should be increased to provide improved targeting and tracking of opposing submarines.

The other way to support ASW in the open ocean is by utilizing MQ-9Bs to support long-range maritime patrols, and there is precedence. During the Second World War, the Army Air Corps utilized B-17s and other aircraft to support ASW patrols from Iceland to the Caribbean to deter German submarines from surfacing. Air Force battle management and other special mission aircraft could play a similar role in finding submarines. Air Force “Compass Call” aircraft could support jamming enemy submarine communications, targeting, and scouting channels. Most submarine over-the-horizon targeting comes from satellite communications. Without those communications, the range of a submarine-launched missile is reduced to the organic targeting distance. This potentially reduces the range from 300 nautical miles to under 50 nautical miles. At those ranges, a carrier strike group’s organic ASW assets have a chance at locating and defeating an enemy submarine.

7. Draw enemy submarines into ASW “kill boxes.” Drawing the enemy into “kill boxes” utilizes joint force capabilities. The theater anti-submarine warfare commander should design kill boxes based on chokepoints, bathymetry, acoustic profiles, and the location of ASW-equipped friendly forces. Integration should be based on sensor and weapons capabilities.

8. Mask our forces from submarine detection or classification. There are several ways that the Navy masks forces from submarine detection or classification. Some of the easiest ways include operating in areas of the ocean with a large amount of acoustic noise, in areas with poor acoustic conditions for the spread of noise, and operating the engineering plant to present different acoustic profiles. Air Force aircraft could drop large noisemaking decoys offset from naval assets to drive enemy submarines away from the naval force. These self-propelled noisemakers are already in the Navy’s inventory as training tools. Noisemakers could also be configured to serve as lures, mimicking the acoustic profiles of worthwhile targets to entice submarines into kill boxes for joint fires prosecution.

Tactical ASW

The joint force plays a role in tactical anti-submarine warfare. The joint force assets used to detect, classify, and track submarines in chokepoints, the open ocean, and kill boxes must also be able to engage the submarine. Equipping littoral regiments and multi-domain task forces to engage submarines is vital as it might represent the last opportunity before the submarine can break into the open ocean.

Task forces comprised of escort carriers played several roles during the Battle of the Atlantic, escorting convoys or participating in hunter-killer groups. World War II task forces utilized signals intelligence to locate and attack German U-boats. Modern reincarnations of the hunter-killer group might include allied frigates, destroyers, and composite squadrons specialized for ASW. For example, the Japanese Mogami class frigate and squadrons composed of MQ-9Bs or MH-60R helicopters operating from Navy flattops like amphibious assault ships or expeditionary sea bases. Queuing would be supported by the federated intelligence apparatus in addition to the organic scouting capabilities of the group.

9. Defeat the submarines in close battle. With the advent of anti-ship cruise missile-armed submarines, the close battle can be anywhere from a few hundred yards to over 300 nautical miles. Supporting the force with ASW-capable aircraft, deploying missile countermeasures, jamming submarine communication and datalink capabilities, or providing intelligence of a missile launch must not be overlooked as meaningful contributions by the joint force. This weaves into the next thread.

10. Defeat the incoming torpedo. This thread should be updated to include defeating incoming missiles and torpedoes. If all else fails, defend. This thread is primarily a local force action, but there are ways the joint force can still contribute. Mines and submarine nets deployed by littoral regiments and other forces around chokepoints or vulnerable waterways can complicate adversarial targeting. Utilizing soft kill options like decoys or tactical air defenses to engage a missile at range can help thwart a long-range missile attack. Lastly, the joint force can provide indications and warnings of adversarial weapon launches to help friendly assets prepare to defend.

Conclusion

The ten threads of full-spectrum ASW provide an excellent path for joint force integration into the ASW Fight. Some retooling may be required to become effective. As the joint force girds itself for a maritime fight, new units in development to support local sea control or denial should not overlook ASW and invest accordingly.

As in the Second World War, defeating the submarine threat would require a whole-of-government approach in close coordination with allies and partners. It is better to start communicating and training for anti-submarine warfare during peacetime rather than unnecessarily expending blood and treasure in wartime. As the military gears up to fight a maritime fight in the Pacific, every service is eager to play a role. There are roles for the joint force, and the U.S. Navy should take advantage by steering other service resources in ways that improve the Navy’s lethality and help win the ASW fight.

LCDR Jason Lancaster is a Surface Warfare Officer. He currently works at OPNAV N5. His last sea tour was as C5I Officer aboard USS AMERICA (LHA 6).  Afloat he has also served as a Destroyer Squadron Operations Officer, Weapons Officer on a DDG, with division officer tours aboard an LSD and an LPD.  Ashore, he has worked in the N5 at OPNAV and Commander, Naval Forces Korea. He is an alumnus of Mary Washington College and holds an MA in History from the University of Tulsa.

The views presented are his own and do not necessarily reflect the official view of the U.S. Government or the Department of Defense.

Featured Image: A PLA Navy submarine attached to a submarine flotilla under the PLA Northern Theater Command bears off a port for the maritime combat training drills on March 23, 2022. (Photo via eng.chinamil.com.cn/photo by Wu Haodong)

Emerging Tech Week

A Roadmap to Successful Sonar AI

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Emerging Technologies Topic Week

By LT Andrew Pfau

Even as the private sector and academia have made rapid progress in the field of Artificial Intelligence (AI) and Machine Learning (ML), the Department of Defense (DoD) remains hamstrung by significant technical and policy challenges. Only a fraction of this civilian-driven progress can be applied to the AI and ML models and systems needed by the DoD; the uniquely military operational environments and modes of employment create unique development challenges for these potentially dominant systems. In order for ML systems to be successful once fielded, these issues must be considered now. The problems of dataset curation, data scarcity, updating models, and trust between humans and machines will challenge engineers in their efforts to create accurate, reliable, and relevant AI/ML systems.

Recent studies recognize these structural challenges. A GAO report found that only 38 percent of private sector research and development projects were aligned with DoD needs, while only 12 percent of projects could be categorized as AI or autonomy research.1 The National Security Commission on Artificial Intelligence’s Final Report also recognizes this gap, recommending more federal R&D funding for areas critical to advance technology, especially those that may not receive private sector investment.2 The sea services face particular challenges in adopting AI/ML technologies to their domains because private sector interest and investment in AI and autonomy at sea has been especially limited. One particular area that needs Navy-specific investment is that of ML systems for passive sonar systems, though the approach certainly has application to other ML systems.

Why Sonar is in Particular Need of Investment

Passive sonar systems are a critical component on many naval platforms today. Passive sonar listens for sounds emitted by ships or submarines and is the preferred tool of anti-submarine warfare, particularly for localizing and tracking targets. In contrast to active sonar, no signal is emitted, making it more covert and the method of choice for submarines to locate other vessels at sea. Passive sonar systems are used across the Navy in submarine, surface, and naval air assets, and in constant use during peace and war to locate and track adversary submarines. Because of this widespread use, any ML model for passive sonar systems would have a significant impact across the fleet and use on both manned and unmanned platforms. These models could easily integrate into traditional manned platforms to ease the cognitive load on human operators. They could also increase the autonomy of unmanned platforms, either surfaced or submerged, by giving these platforms the same abilities that manned platforms have to detect, track, and classify targets in passive sonar data.

Passive sonar, unlike technologies such as radar or LIDAR, lacks the dual use appeal that would spur high levels of private sector investment. While radar systems are used across the military and private sector for ground, naval, air, and space platforms, and active sonar has lucrative applications in the oil and gas industry, passive sonar is used almost exclusively by naval assets. This lack of incentive to invest in ML technologies related to sonar systems epitomizes the gap referred to by the NSC AI report. Recently, NORTHCOM has tested AI/ML systems to search through radar data for targets, a project that has received interest and participation from all 11 combatant commands and the DoD as a whole.3 Due to its niche uses, however, passive sonar ML systems cannot match this level of department wide investment and so demands strong advocacy within the Navy.

Dataset Curation

Artificial Intelligence and Machine Learning are often conflated and used interchangeably. Artificial Intelligence refers a field of computer science interested in creating machines that can behave with human-like abilities and can make decisions based on input data. In contrast, Machine Learning, a subset of the AI filed, refers to computer programs and algorithms that learn from repeated exposure to many examples, often millions, instead of operating based on explicit rules programmed by humans.4 The focus in this article is on topics specific to ML models and systems, which will be included as parts in a larger AI or autonomous system. For example, an ML model could classify ships from passive sonar data, this model would then feed information about those ships into an AI system that operates an Unmanned Underwater Vehicle (UUV). The AI would make decisions about how to steer the UUV based on data from the sonar ML model in addition to information about mission objectives, navigation, and other data.

Machine learning models must train on large volumes of data to produce accurate predictions. This data must be collected, labeled, and prepared for processing by the model. Data curation is a labor- and time-intensive task that is often viewed as an extra cost on ML projects since it must occur before any model can be trained, but this process should be seen as an integral part of ML model success. Researchers recently found that one of the most commonly used datasets in computer vision research, ImageNet, has approximately 6 percent of their images mislabeled 5. Another dataset, QuickDraw, had 10 percent of images mislabeled. Once the errors were corrected, model performance on the ImageNet dataset improved by 6 percent over a model trained on the original, uncorrected, dataset.5

For academic researchers, where the stakes of an error in a model are relatively low, this could be called a nuisance. However, ML models deployed on warships face greater consequences than those in research labs. A similar error, of 6 percent, in an ML model to classify warships would be far more consequential. The time and labor costs needed to correctly label data for use in ML model training needs to be factored into ML projects early. In order to make the creation of these datasets cost effective, automatic methods will be required to label data, and methods of expert human verification must ensure quality. Once a large enough dataset has been built up, costs will decrease. However, new data will still have to be continuously added to training datasets to ensure up to date examples are present in the training of models.

A passive acoustic dataset is much more than an audio recording: Where and when the data is collected, along with many other discrete factors, are also important and should be integrated into the dataset. Sonar data collected in one part of the ocean, or during a particular time of year, could be very different than other parts of the ocean or the same point in the ocean at a different time of year. Both the types of vessels encountered and the ocean environment will vary. Researchers at Brigham Young University demonstrated how variations in sound speed profiles can affect machine learning systems that operate on underwater acoustic data. They showed the effects of changing environmental conditions when attempting to classify seabed bottom type from a moving sound source, with variations in the ability of their ML model to provide correct classifications by up to 20 percent.6 Collecting data from all possible operating environments, at various times of the year, and labeling them appropriately will be critical to building robust datasets from which accurate ML models can be trained. Metadata, in the form of environmental conditions, sensor performance, sound propagation, and more must be incorporated during the data collection process. Engineers and researchers will be able to analyze metadata to understand where the data came from and what sensor or environmental conditions could be underrepresented or completely missing.

These challenges must be overcome in a cost-effective way to build datasets representative of real world operating environments and conditions.

Data Scarcity

Another challenge in the field of ML that has salience for sonar data are the challenges associated with very small, but important datasets. For an academic researcher, data scarcity may come about due to the prohibitive cost of experiments or rarity of events to collect data on, such as astronomical observations. For the DoN, these same challenges will occur in addition to DoN specific challenges. Unlike academia or the private sectors, stringent restrictions on classified data will limit who can use this data to train and develop models. How will an ML model be trained to recognize an adversary’s newest ship when there are only a few minutes of acoustic recording? Since machine learning models require large quantities of data, traditional training methods will not work or result in less effective models.

Data augmentation, replicating and modifying original data may be one answer to this problem. In computer vision research, data is augmented by rotating, flipping, or changing the color balance of an image. Since a car is still a car, even if the image of the car is rotated or inverted, a model will learn to recognize a car from many angles and in many environments. In acoustics research, data is augmented by adding in other sounds or changing the time scale or pitch of the original audio. From a few initial examples, a much larger dataset to train on can be created. However, these methods have not been extensively researched on passive sonar data. It is still unknown which methods of data augmentation will produce the best results for sonar models, and which could produce worse models. Further research into the best methods for data augmentation for underwater acoustics is required.

Another method used to generate training data is the use of models to create synthetic data. This method is used to create datasets to train voice recognition models. By using physical models, audio recordings can be simulated in rooms of various dimensions and materials, instead of trying to make recordings in every possible room configuration. Generating synthetic data for underwater audio is not as simple and will require more complex models and more compute power than models used for voice recognition. Researchers have experimented with generated synthetic underwater sounds using the ORCA sound propagation model.6 However, this research only simulated five discrete frequencies used in seabed classification work. A ship model for passive sonar data will require more frequencies, both discrete and broadband, to be simulated in order to produce synthetic acoustic data with enough fidelity to use in model training. The generation of realistic synthetic data will give system designers the ability to add targets with very few examples to a dataset.

The ability to augment existing data and create new data from synthetic models will create larger and more diverse datasets, leading to more robust and accurate ML models.

Building Trust between Humans and Machines

Machine learning models are good at telling a human what they know, which comes from the data they were trained on. They are not good at telling humans that they do not recognize an input or have never seen anything like it in training. This will be an issue if human operators are to develop trust in the ML models they will use. Telling an operator that it does not know, or the degree of confidence a model has in its answer, will be vital to building reliable human-machine teams. One method to building models with the ability to tell human operators that a sample is unknown is the use of Bayesian Neural Networks. Bayesian models can tell an operator how confident they are in a classification and even when the model does not know the answer. This falls under the field of explainable AI, AI systems that can tell a human how the system arrived at the classification or decision that is produced. In order to build trust between human operators and ML systems, a human will need some insight into how and why an ML system arrived at its output.

Ships at sea will encounter new ships, or ships that were not part of the model’s original training dataset. This will be a problem early in the use of these models, as datasets will initially be small and grow with the collection of more data. These models cannot fail easily and quickly, they must be able to distinguish between what is known and what is unknown. The DoN must consider how human operators will interact with these ML models at sea, not just model performance.

Model Updates

To build a great ML system, the models will have to be updated. New data will be collected and added to the training dataset to re-train the model so that it stays relevant. In these models, only certain model parameters are updated, not the design or structure of the model. These updates, like any other digital file can be measured in bytes. An important question for system designers to consider is how these updates will be distributed to fleet units and how often. One established model for this is the Acoustic- Rapid COTS Insertion (ARCI) program used in the US Navy’s Submarine Force. In the ARCI program, new hardware and software for sonar and fire control is built, tested, and deployed on a regular, two-year cycle.7 But two years may be too infrequent for ML systems that are capable of incorporating new data and models rapidly. The software industry employs a system of continuous deployment, in which engineers can push the latest model updates to their cloud-based systems instantly. This may work for some fleet units that have the network bandwidth to support over the air updates or that can return to base for physical transfer. Recognizing this gap, the Navy is currently seeking a system that can simultaneously refuel and transfer data, up to 2 terabytes, from a USV.8 This research proposal highlights the large volume of data will need to be moved, both on and off unmanned vessels. Other units, particularly submarines and UUVs, have far less communications bandwidth. If over-the-air updates to submarines or UUVs are desired, then more restrictions will be placed on model sizes to accommodate limited bandwidth. If models cannot be made small enough, updates will have to be brought to a unit in port and updated from a hard drive or other physical device.

Creating a good system for when and how to update these models will drive other system requirements. Engineers will need these requirements, such as size limitations on the model, ingestible data type, frequency of updates needed by the fleet, and how new data will be incorporated into model training before they start designing ML systems.

Conclusion

As recommended in the NSC AI report, the DoN must be ready to invest in technologies that are critical to future AI systems, but that are currently lacking in private sector interest. ML models for passive sonar, lacking both dual use appeal and broad uses across the DoD, clearly fits into this need. Specific investment is required to address several problems facing sonar ML systems, including dataset curation, data scarcity, model updates, and building trust between operators and systems. These challenges will require a combination of technical and policy solutions to solve them, and they must be solved in order to create successful ML systems. Addressing these challenges now, while projects are in a nascent stage, will lead to the development of more robust systems. These sonar ML systems will be a critical tool across a manned and unmanned fleet in anti-submarine warfare and the hunt for near-peer adversary submarines.

Lieutenant Andrew Pfau, USN, is a submariner serving as an instructor at the U.S. Naval Academy. He is a graduate of the Naval Postgraduate School and a recipient of the Rear Admiral Grace Murray Hopper Computer Science Award. The views and opinions expressed here are his own.

Endnotes

1. DiNapoli, T. J. (2020). Opportunities to Better Integrate Industry Independent Research and Development into DOD Planning. (GAO-20-578). Government Accountability Office.

2. National Security Commission on Artificial Intelligence (2021), Final Report.

3. Hitchens, T. (2021, July 15) NORTHCOM Head To Press DoD Leaders For AI Tools, Breaking Defense, https://breakingdefense.com/2021/07/exclusive-northcom-head-to-press-dod-leaders-for-ai-tools/

4. Denning, P., Lewis, T. Intelligence May Not be Computable. American Scientist. Nov-Dec 2019. http://denninginstitute.com/pjd/PUBS/amsci-2019-ai-hierachy.pdf

5. Hao, K. (2021, April 1) Error-riddled data sets are warping our sense of how good AI really is. MIT Technology Review. https://www.technologyreview.com/2021/04/01/1021619/ai-data-errors-warp-machine-learning-progress/

6. Neilsen et al (2021). Learning location and seabed type from a moving mid-frequency source. Journal of the Acoustical Society of America. (149). 692-705. https://doi.org/10.1121/10.0003361

7. DeLuca, P., Predd, J. B., Nixon, M., Blickstein, I., Button, R. W., Kallimani J. G., and Tierney, S. (2013) Lessons Learned from ARCI and SSDS in Assessing Aegis Program Transition to an Open-Architecture Model, (pp 79-84) RAND Corperation, https://www.jstor.org/stable/pdf/10.7249/j.ctt5hhsmj.15.pdf

8. Office of Naval Research, Automated Offboard Refueling and Data Transfer for Unmanned Surface Vehicles, BAA Announcement # N00014-16-S-BA09, https://www.globalsecurity.org/military/systems/ship/systems/oradts.htm

Featured Image: Sonar Technician (Surface) Seaman Daniel Kline performs passive acoustic analysis in the sonar control room aboard the guided-missile destroyer USS Ramage (DDG 61). (U.S. Navy photo by Mass Communication Specialist 2nd Class Jacob D. Moore/Released)

Tactics

Close the Gaps! Airborne ASW Yesterday and Tomorrow

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By Jason Lancaster, LCDR, USN

Introduction

Anti-submarine warfare (ASW) is about putting sensors and weapons in place to detect and destroy submarines. The types of sensors have changed based on technological improvements and types of submarines, but the main principle is minimizing the sensor coverage gaps and engaging the submarine before it is within its weapons engagement zone (WEZ). Speed, endurance, and flexibility make aircraft excellent ASW platforms. It enables them to conduct wide-area searches and engage submarines before a submarine can attack.

Airpower is vital to protecting the center of gravity. In the Second World War, the European naval war’s center of gravity was the trans-Atlantic convoys that supplied the Allies’ war effort. The Allied struggle was to reduce air coverage gaps in the Atlantic to effectively protect convoys. In order to convoy ships across the Atlantic, the Allies had to close the gaps in air coverage. During the Cold War Era, the center of gravity was the power projection capability of the carrier. The challenge was to protect the carrier both for convoy protection and force projection. Today, the challenge to protect the carrier remains, and a dangerous new gap needs to be closed.

The Russian and Chinese navies have invested heavily in building quiet submarines capable of firing Anti-Ship Cruise Missiles (ASCMs) in excess of 200 nm. These missiles threaten our Carrier Strike Groups (CSGs) because the CSG lacks an organic capability to detect and engage these submarines outside of the submarines’ WEZ. This is not the first time that we have dealt with an increasingly dangerous submarine threat. Today, the U.S. center of gravity for naval combat remains the CVN. To defend the CVN or any high value vessels from submarines, we may find the answer to be similar to what it was in World War II and the Cold War. We can explore the U.S. Navy’s historical use of air power and technology to overcome submarine advantages and then explore future improvements to close the gaps using unmanned aircraft.  

The Second World War

The Battle of the Atlantic tested the Allies’ ability to defend trans-Atlantic convoys at points throughout the European Theater of Operations, from Archangel to Cape Town and the Panama Canal to the Suez Canal; convoys had to be protected from submarines. Allied victory in the Battle of the Atlantic was the result of the Allies’ ability to eliminate gaps in air coverage with long range air and carrier-based convoy escorts. The challenge for the Allies was to extend air coverage to cover the entire convoy route. The Allies closed air coverage gaps in three ways: they expanded the number of air stations, developed longer-range aircraft, and integrated the escort carrier (CVE).

In August 1942, aircraft were limited to proximity from the U.S., Canada, Iceland, Northern Ireland, Gibraltar, and the African coast. Air coverage decreased the number of attacks in the western approaches to the English Channel. However, the German U-boats continued their depredations farther to sea into an area where aircraft could not reach. The Navy had to continue to close coverage gaps.

In order to close gaps, the Navy went to work opening air bases around the Atlantic rim to expand air coverage. From Greenland to Brazil, the U.S. worked with host nations to build and develop airfields. Unfortunately, gaining permission to operate an airfield did not mean planes could start flying right away. For example, the Danish government in exile gave the United States permission to operate aircraft out of Narsarsuaq, Greenland in April 1941; VP-6 aircraft did not operate from there until October 1943. In Natal, Brazil, the Navy took over facilities that Pan Am had been developing in 1940, but the facilities did not officially become active until 1943. In the Caribbean, planes flew convoy routes from Coco Solo, Panama to Trinidad and on to San Juan, Puerto Rico.

Extent of Allied Air Coverage (Author Graphic)

The Navy acquired the bases to operate from, but to close the gaps, aircraft were required to patrol from those bases. The Navy began the war with long-range aircraft, but not the vast numbers required for the massive amount of ocean requiring protection. Thousands of hours of patrol time were required to detect a submarine, creating a massive demand for aircraft. Congress passed the Two Ocean Navy Act in 1940, but aircraft production and aviation training had to catch up to wartime demand. 49 fixed-wing patrol (VP) squadrons were formed in 1943 alone. The influx of new planes and aircrews allowed the Allies to swarm the Atlantic.

This influx of planes enabled the Navy to cover the Atlantic in aircraft and force the U-boats to change tactics. In 1940, U-boats had submerged at the first sight of an aircraft. Many of those aircraft lacked effective weapons to sink a U-boat. Improvements to depth charges, radar, and searchlights increased the kill count. By 1943, U-boats had been re-armed with quadruple 20 mm anti-aircraft guns and traveled the Bay of Biscay surfaced in packs for mutual defense against aircraft. Submarines shooting it out with aircraft resulted in the sinking of 34 submarines in the Atlantic in July 1943. Between August and December of 1943, the Allies flew 7,000 hours of patrols in the Bay of Biscay alone. 7,000 hours translated to 36 sightings, 18 attacks, and 3 kills. Although the number of sightings was low, the U-boats had implemented a policy of maximum submergence, reducing their ability to travel rapidly on the surface during daylight.

Despite increased bases and more aircraft, the center of the Atlantic remained out of reach to land-based aircraft. This gap was closed by escort carriers (CVEs). These aircraft carriers were converted from merchant ships and equipped with a flight deck and a composite squadron of approximately 20 carrier aircraft; typically F4F Wildcats and TBF Avengers. Escort carriers operated in two main modes; direct support to convoys flying patrols around the convoy searching for U-boats, or as the flagship of a hunter-killer squadron. Initially, the aircraft only flew daytime missions, but submarines would surface to recharge their batteries at night. The aircraft flying off escort carriers became the first to regularly fly night missions. Escort carrier groups sank 53 U-boats during the war, including 60 percent of all U-boats sank between April and September of 1944.

A torpedo plane approaches for a landing while USS Guadalcanal tows U-505 astern. (U.S. Navy photo)

By June 1944, U-boats operated primarily submerged utilizing snorkels. The Allies’ ability to build airbases, manufacture planes, and convert aircraft carriers from merchant ships had enabled them to patrol the entirety of the Atlantic, giving the U-boats nowhere to escape.  Staying submerged dramatically reduced submarine range and speed, and there were more U-boat losses than merchant ship losses by the end of 1944. Closing the air coverage gaps in the Atlantic enabled the United States to transport armies across the ocean, maintain the supply lines to the Soviet Union and Great Britain, and win victory in Europe.     

The Cold War

During the Cold War, the Navy focused resources into the ability to project power ashore by building carrier battle groups and operating them in the eastern Mediterranean and the high north. The Cold War carrier battle group had to contend with Soviet long-range naval aviation, as well as nuclear and diesel submarines. Protecting the carrier against nuclear and diesel-electric submarines required defense-in-depth to prevent coverage gaps where submarines could freely target the carrier.

In the early years of the Cold War, World War II-era aircraft carriers were converted to ASW carriers (CVS) and operated 20 S-2 Trackers and 16-18 ASW helicopters and their escorts. During the 1950s, the U.S. maintained 20 ASW battle groups composed of a CVS and escorts. Budget constraints, a focus on the Vietnam War, and the increasing maintenance costs of aging ships resulted in the decommissioning of CVSs through the late 1960s. To maintain carrier-based airborne ASW, the CV replaced an attack squadron (VA) with an air ASW squadron (VS).

Exercises such as Ocean Venture ’81 had demonstrated the Navy’s global reach and ability to place strike aircraft on the Soviet border undetected. The Soviets wanted to deny the eastern Mediterranean and the high north to carrier battle groups to protect the Soviet Union from these attacks. The Soviets’ primary means of denial were their massive submarine fleet and long-range aviation assets. The U.S. expected the Soviets to attack the convoy routes that would bring additional U.S. troops, equipment, and stores to Europe, as well as target the carrier battle groups.  

The U.S. developed an ASW system to protect both convoys and battle groups. Submarines and maritime patrol reconnaissance aircraft (MPRA) could patrol independently, but also received cueing from the Sound Surveillance System (SOSUS). SOSUS arrays stretched across the gaps that Soviet submarines would travel to reach the north Atlantic Ocean; from Bear Island to the Norwegian coast, and across the Greenland-Iceland-UK gaps (GIUK). These arrays were monitored by acoustic technicians and able to vector submarines and MPRA to pounce on Soviet submarines as they transited into the north Atlantic. These barriers formed the outer submarine defensive zones that would enable the U.S. to kill Soviet submarines in chokepoints. The role of these submarines and MPRA was sea denial.

A U.S. Navy Lockheed P-3C Orion from Patrol Squadron Eight (VP-8) “Fighting Tigers” flying over a Soviet Victor III-class submarine in 1985.(U.S. Navy photo)

Convoys would be supported by helicopter-equipped ASW frigates and destroyers and MPRA operating from bases in Canada, Iceland, the Azores, and the United Kingdom. The mission of these escorts was not to create permanent sea control, but to create a bubble of temporary local sea control that would enable the convoyed merchant ships to reach Europe without losses. Carrier battle groups would support these convoys, as required, to protect against air attacks, or would head to the Norwegian coast to conduct offensive operations against the Soviet Union.  

The purpose of the carrier battle group was sea control. The typical carrier battle group was composed of an aircraft carrier, 8-10 escorting cruisers, destroyers, and frigates, and the air wing. The carrier battle group utilized defense-in-depth to defend the carrier. The most distant ring was the inorganic theater ASW (TASW) fight utilizing the SOSUS network, MPRA, and submarines. The battle group did not lead this fight, but paid attention to it.  

Submarines that transited past the MPRA, submarine, and SOSUS barriers required the battle group’s anti-submarine warfare commander (ASWC) to defend the carrier. The 1980s battle group’s ASW plan was composed of three zones: the outer zone (100-300NM), the middle zone (30-70NM), and the inner zone (0-30NM). The battle group’s organic outer defense was composed of ASW helicopter-equipped frigates or destroyers with towed acoustic arrays. The VS squadron and helicopter anti-submarine squadron (HS) were to patrol the inner and middle zones, but maintained the ability to pounce in the outer zone, as required. The inner screen was composed of 3-4 destroyers or frigates utilizing active sonar. Active sonar was required because the carrier and its inner screen utilized speed and maneuver to minimize the ability of a submarine to target the carrier. The noise of speed negated passive tracking.

September 9, 1989 – A starboard quarter view of a Soviet Akula Class nuclear-powered attack submarine underway. (Photo via U.S. National Archives)

Victory for the TASW MPRA, submarine, and SOSUS team was the number of submarines destroyed. The battle group’s victory was defined avoiding an attack, whether that was from killing submarines, utilizing limiting lines of approach and maneuver, or defense-in-depth deterrence to prevent submarines from closing on the carrier. The Navy utilized multiple assets with different capabilities and limitations to prevent gaps in the carrier’s screen. TASW, multiple surface ships, CV, DD, and FF-based helicopters and ASW aircraft all contributed to the successful defense of the carrier. The skilled ASWC was able to balance the strengths and weaknesses of each part of the screen and keep the Soviet submarine away from the carrier.

ASW Today and Tomorrow

The threat of Soviet submarines seemingly disappeared with the collapse of the Soviet Union. Without the threat of Soviet submarines, U.S. interest in ASW withered. The nation’s peace dividend included the cancellation of the P-3 replacement aircraft, and the reduction of MPRA squadrons from 24 to 12 between 1989 and 1996. The remaining P-3s found their sensors optimized for detecting surfaced submarines and were useful to the Joint Force flying ISR missions over the Balkans and the Middle East. These missions sustained the reduced MPRA force through the budget cuts of the 1990s and the land combat-centric days of the War on Terror. The S-3B Vikings left their ASW role behind and performed mission tanking duties for F/A-18s before being prematurely retired, many with almost 10,000 flying hours left in them.  

In the 2010s, a new generation of ASW aircraft was flying. The P-8A Poseidon replaced the P-3C Orion and the MH-60R replaced the SH-60B and SH-60F. As witnessed during multiple ASW exercises, the combination of P-8As and MH-60Rs is nearly unstoppable. However, there is a clear capability gap at the strike group level. As a theater asset, the P-8s are limited in number, and fly missions across the fleet. The MH-60R has tremendous capability, but a limited range. It is not designed for area searching, but localizing a contact or conducting datum searches.

Full Spectrum ASW’s 9th thread is, “defeat the submarine in close battle.” With modern ASCMs and over-the-horizon targeting, the close battle is at least 200 nm from the strike group. The strike group must rely on the theater ASW commander to prosecute any modern submarines. While the strike group is important for the TASW commander to protect, TASW has a limited number of available submarines and P-8s and a multitude of submarines to prosecute. An organic aircraft capable of long-range ASW would enable the strike group commander to defend a larger strike group operating area, freeing TASW assets for threads 5 (Defeat submarines in choke points), 6 (Defeat submarines in open ocean), and 7 (Draw the enemy into ASW “kill boxes”).

Today, the CSG is composed of an aircraft carrier and three to five escorting cruisers or destroyers, which is half the ships of a Cold War-era Carrier Battle Group, and an air wing. The main organic ASW aircraft are MH-60Rs, helicopters with outstanding capabilities, but limited range. There are no organic ASW aircraft in the carrier air wing capable of searching, localizing, tracking, and engaging submarines beyond the submarine’s WEZ.  

MH-60Rs were not designed for area ASW searches and lack the endurance to search 200 nm from their ship. E-2 and EA-18G aircraft support the ASW fight with their capable radar and electronic warfare suites when the submarine is surfaced, or utilizing a periscope or radar. F-18s, C-2s, and MH-60Ss support primarily through visual search for submarines as they fly around the carrier. But searching for submarines visually or when surfaced are hardly ideal tactics.

Reducing the inner screen in order to get a ship out far enough to conduct a search in the outer zone is incredibly risky. A compelling solution is to establish an unmanned sea control squadron (VUS) squadron. These squadrons would provide Sea Combat Commanders with a dedicated medium-range ASW aircraft that would allow commanders to detect, classify, track, target, and engage submarines outside their WEZ. Everything the aircraft needs already exists. Equip a carrier-capable UAV with Forward Looking Infrared cameras (FLIR), AN/APS 153 radar, and ALQ-210 Electronic Support Measures systems from the MH-60R, LINK-16, active, passive, and Multi-Static Active Coherent (MAC) sonar buoys, and arm it with Mk 54 torpedoes and air-launched ASCMs.

This capable aircraft would directly support the Carrier Strike Group and enable it to engage submarines outside their WEZ. The technology exists. In order to protect the carrier today, the Navy needs to continue to close the gaps.

LCDR Jason Lancaster is a U.S. Navy Surface Warfare Officer. He has served aboard amphibious ships, destroyers, and as operations officer of a destroyer squadron. He is an alumnus of Mary Washington College and holds a Master’s Degree in History from the University of Tulsa. His views are his alone and do not represent the stance of any U.S. government department or agency.

Bibliography

Atkins, R.W. “ASW: Where is the Inner Screen?” Naval War College Review, January-February 1982: 48-49.

Barlow, Jeffrey. “The Navy’s Escort Carrier Offensive.” Naval History Magazine, November 2013.

Bernard, Colin. “Nobody Asked Me… But Bring Back the S-3 Viking.” Proceedings, January 2018.

Byron, John. “The Victim’s View of ASW.” Proceedings, April 1982.

Cote, Owen. The Third Battle of the Atlantic: Innovation in the U.S. Navy’s Silent Cold War Struggle with Soviet Submarines. Newport, Rhode Island: Naval War College Press, 2012.

Foggo, James, and Alarik Fritz. “The Fourth Battle of the Atlantic.” Proceedings, June 2016.

Friedman, Norman. “World Naval Developments: More Than a Tanker?” Proceedings, October 2018.

Frigge, William. “Winning Battle Group ASW.” Proceedings, October 1987.

Metrick, Andrew. “(Un)Mind the Gap.” Proceedings, October 2019.

Middleton, Drew. “U.S. AND ALLIED NAVIES STARTING MAJOR TEST TODAY.” New York Times, August 1, 1981: 1.

Naval History and Heritage Command. “Dictionary of American Naval Aviation Squadrons Volume 2.” The History of VP, VPB, VP(H) and VP(AM) Squadrons. Edited by Naval History and Heritage Command. Naval History and Heritage Command. n.d. https://www.history.navy.mil/research/histories/naval-aviation-history/dictionary-of-american-naval-aviation-squadrons-volume-2.html (accessed May 28, 2020).

Shugart, Thomas. “Build All-UAV Carriers.” Proceedings, September 207.

Stavridis, James. “Creating ASW Killing Zones.” Proceedings, October 1987.

Sternhell, Charles, and Alan Thorndike. OEG Report No 51: Anti-Submarine Warfare in World War II. Washington DC: Navy Department, 1946.

Toti, William J. “The Hunt for Full Spectrum ASW.” Proceedings, June 2014.

Voss, Philip. “Battle Force ASW: M3.” Proceedings, January 1989.

Wedewer, Harry. “Scout from the Sea.” Proceedings, September 1999.

Featured Image: An S-3 Viking and A-6 Intruder from the USS John F. Kennedy (CV-67) fly over a Soviet Foxtrot class diesel submarine. (U.S. Navy photo)

Capability Analysis, Indo-Asia-Pacific

Undersea Surveillance: Supplementing the ASEAN Indo-Pacific Outlook

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By Shang-su Wu 

The recently announced Indo-Pacific Outlook by the Association of Southeast Asian Nations (ASEAN) at the 34th Summit indicates the Southeast Asian perspective on the evolving geostrategic environment. Unsurprisingly, ASEAN highlights cooperation, stability, peace, freedom of navigation and other values in the statement. The Outlook, however, leaves a question: how will ASEAN protect these values when diplomatic measures fail?

Under the ASEAN way, it would not be realistic to expect strong words such as those implying the use of force in any official statement, but member countries bordering critical straits could indirectly convey the message by demonstrating relevant defense capabilities. Among a variety of defense capabilities, tracking foreign submarines through enhanced undersea surveillance could be a relevant option.

Tracking Submarines

The major strategic significance of Southeast Asia in the Indo-Pacific region is mostly found in several critical sea lanes where various powers’ military assets travel through channels connecting the two oceans. Under the United Nations Convention on the Law of the Sea (UNCLOS), military vessels and aircraft enjoy the right of innocent passage through these sea routes, whether classified as international straits or archipelagic waters, and coastal countries track these movements. Modern technology makes it feasible for coastal states to readily track foreign military aircraft and surface vessels, a task that is more about safety than security. But tracking submerged submarines is another matter with a much higher barrier to entry.

In the face of complicated hydrographic conditions along with the improving stealth of submarines, there are high requirements for detection in terms of sonars, training, joint operations, and other elements of undersea surveillance. Therefore, successfully tracking submarines requires a high degree of military professionalism and capability. But once successfully tracked and trailed, a submarine receives a clear but private message of deterrence.

Silent Deterrence

This kind of covert deterrence would fit the geopolitical context in Southeast Asia. Firstly, it is generally legitimate for a littoral state to detect underwater entities because submarines should sail on the surface during innocent passage in territorial waters, while a submerged transit is acceptable under UNCLOS in passing sea routes and international straits. But only when a littoral state can identify the locations of foreign submarines transiting underwater can it determine whether UNCLOS is violated or obeyed. In other words, Southeast Asian countries have a sovereign right and legal obligation toward undersea surveillance. 

Tracking submerged submarines also presents a credible level of readiness for uncertainty. Overt exercises can be tailored for specific scenarios to prove certain levels of joint operations and other tactical skills, while bilateral and multilateral exercises highlight partnership, alliance, and other interstate security ties. Exercises are often much broader than the single capability of tracking submarines. Exercises, however, are either fully or semi-planned, and tracking foreign submarines is a truly dynamic encounter between two sides without an advance arrangement. Furthermore, Southeast Asian countries already have routinely conducted various bilateral and multilateral exercises with regional and extra-regional counterparts.

Tracking submerged submarines is usually beyond the microscope of conventional and social media, and can avoid the open hostility or other forms of public outcry that often transpire after close encounters between surface vessels. As the detecting side can deny any information on the tracking, publicity of the event would be more controllable compared with open statements or actions. For the country of the tracked submarine, such encounters are usually negative for national pride and military professionalism, so decision-makers would not have much incentive for revealing the encounter.  

Improving Hardware and Challenges Ahead

Since the end of the Cold War, Southeast Asian navies, particularly those of Indonesia, Malaysia, and Singapore, have built up their anti-submarine warfare (ASW) capabilities, including through several types of undersea sensors. These three countries have acquired survey vessels to establish their individual hydrographic databases. They have also procured state-of-the-art anti-submarine warfare helicopters such as the Super Lynx, S-70B, and AS-565MBe and deployed them on their respective frigates and corvettes which have towed or hull-mounted sonars. Furthermore, all three navies possess submarines to play the role of targets during training.

SOUTH CHINA SEA (June 18, 2013) A Royal Malaysian Navy Super Lynx prepares to land on the flight deck of USS Freedom (LCS 1) during deck landing qualifications (DLQs). (U.S. Navy photo by Mass Communication Specialist 1st Class Cassandra Thompson/Released)

Some characteristics impose challenges on the ability of Southeast Asian countries to track submarines. Large areas of territorial waters are natural obstacles for Malaysia and Indonesia. The numbers of maritime survey vessels they have in service are rather small for accumulating and updating their hydrographic data. By the same token, these two countries’ sensors and platforms, including ASW helicopters or ships, are likely not numerous enough to cover their broad territories or responsively deploy to where contacts are found.

Thanks to its tiny size, Singapore’s assets cannot be geographically diluted, but it shares other constraints with its neighbors, including a lack of fixed-wing ASW aircraft. The Indonesian CN-235 and the Singaporean Fokker-50 maritime patrol aircraft (MPA) only have limited ASW capabilities, and Malaysia’s smaller Beech-200 MPAs have no payload space for ASW weapons. Finally, operational experience is another common challenge for these three countries, as they began to introduce their sophisticated ASW assets mainly in the post-Cold War era where opportunity for practice was slim. 

Currently, the three navies are on a trajectory of improving their ASW capabilities, such as through the towed sonar arrays found in Malaysia’s upcoming frigates and Indonesia’s plan of building underwater surveillance systems. These efforts would gradually make tracking foreign submarines underwater more feasible in the foreseeable future.

Conclusion

Unlike in the Cold War-era, some Southeast Asian countries, especially these three bordering critical straits, do not have empty arsenals. Although their defense capability is still inferior to most extra-regional powers, some wise and tailored applications of their military assets would support ASEAN agenda’s beyond diplomatic and economic means. Successful tracking foreign submarines would make the ASEAN Outlook more valid in the Indo-Pacific geostrategic landscape.

Shang-su Wu is a research fellow at the S. Rajaratnam School of International Studies (RSIS), Nanyang Technological University in Singapore.

Featured Image: A Chinese submarine transits in the Yellow Sea (Wikimedia Commons)