The Coastwatchers: Intelligence Lessons Learned for the Future Single Naval Battle

Naval Intelligence Topic Week

By Captain Michael Van Liew, USMC

The legendary Coastwatchers of World War II provided some of the most critical intelligence of the entire war. Through preparation and effort in the worst of conditions, these units created a reconnaissance screen throughout the South Pacific that was indispensable in the success of the Allies’ single naval battle. The United States Marine Corps describes the single naval battle concept, “Approaching the maritime domain as a singular battlespace (containing land, sea, air and cyber components) offers opportunities through a single naval battle approach that integrates all elements of sea control and naval power projection into a cohesive whole.”1 Today’s increasingly dynamic and complex security environment creates an imperative for the implementation of the single naval battle concept. The single naval battle seeks to remove artificial seams and create a multi-domain naval force that outmatches an increasingly sophisticated adversary in the application of naval power.2 The Coastwatchers intelligence network is one of the greatest intelligence operations of World War II with multiple lessons for future naval intelligence operations in the single naval battle.

Following World War I, Australia and New Zealand each began building an intelligence network along their coastlines and the archipelagos of the South Pacific. The Royal Australian Navy viewed the chain of islands north of Australia, “as a fence, but a fence with several gates; the straits between the islands.”3 This concept became the reconnaissance screen of the Coastwatchers. The Australian Coastwatchers were known as Operation Ferdinand, after the children’s book character Ferdinand the Bull. The name was, “a reminder to them that it was not their duty to fight, and thus draw attention to themselves… it was their duty to sit, circumspectly and unobtrusively, and gather information. Of course, like Ferdinand, they could fight if they were stung.”4 Together, the interlocked Australian and New Zealand Coastwatching networks spanned from New Guinea in the northwest to the Pitcairn Islands in the east.5 The tele radios and existing radio stations that connected these locations enabled a time advantage in intelligence communication, contributing to the Allies’ success in many battles. The networks provided the Allies with a vast intelligence capability for naval operations in the Pacific.

Illustration by the author, map via the CIA World Factbook, depicting the extent of the Australian and New Zealand Coastwatching Networks. The networks created a reconnaissance screen in the South Pacific that supported naval operations to great effect. This reconnaissance screen collected naval intelligence on ship movements, air movements, terrain, hydrography, and activity on the islands. Pitcairn Island, the outlier, while not a part of the reconnaissance screen served an important role in the retransmission and surveillance of transiting ships in that area of the Pacific Ocean. (Click to expand)6

The Coastwatchers’ intelligence served as an integral part of the single naval battle. Admiral Halsey, the commander of the South Pacific Area summarized the Coastwatchers’ effectiveness in the single naval battle during the Solomon Islands Campaign when he stated, “The Coastwatchers saved Guadalcanal, and Guadalcanal saved the South Pacific.”7 The ingenuity and impact of the Coastwatchers during World War II in the Pacific is profound.

Both the Australian and New Zealand Coastwatcher networks were proactive in establishing themselves during the interwar years. The Australian Coastwatcher network began in 1919 and New Zealand began its Coastwatching program in 1929.8 Although the Coastwatchers effort was expanded when war began, the early action taken to create the Coastwatchers proved valuable when war broke out in 1939 and as Japan joined the Axis powers in 1940. Commander Eric Feldt of the Royal Australian Navy served as the Supervising Intelligence Officer of Operation Ferdinand’s Northeast Area for several years.9 He summarizes the importance of a proactive intelligence network, “by September 1939, the Coastwatchers were eight hundred strong, the great majority of them, of course, on the Australian mainland. In Australia’s island screen, where Ferdinand was eventually to operate, the system was still very thin and spotty, but at least a nucleus existed, and funds were available. Upon the outbreak of war… the Navy directed the organization, such as it was, to commence functioning.”10 Predicting the next war has historically been next to impossible, but as the Coastwatchers demonstrate, actively preparing intelligence during periods absent of major conflict assists in preparing for the next major conflict.

Naval intelligence must be proactive to be effective across the competition continuum. In other words, the naval force must always be collecting intelligence. Just as conflict is continuous in its different forms so is the single naval battle and the necessity for continuous intelligence. The United States Marine Corps states, “The integrated single naval battle begins with the Phase 0 battle for influence, allowing discriminating force application based on understanding gained from forward presence.”11 Proactive intelligence achieves this “understanding gained from forward presence.”12 Continuous intelligence collection is necessary for a navy in performing its functions across the range of enduring competition, whether that be in relative peace or relative war.

The Coastwatchers network was effective in serving as a deep sensor by providing multi-domain intelligence collection of the sea, air, and land through human intelligence.13 The value of this multi-domain intelligence collection was demonstrated when the Coastwatchers provided strategic intelligence of the Japanese building an airfield on Guadalcanal. This intelligence focused the United States’ first major naval offensive toward the Solomon Islands Campaign because the airfield posed a threat to the sea lines of communication leading to Australia. During the execution of the campaign, Henderson Field on Guadalcanal provided an “unsinkable aircraft carrier” that kept the Japanese from mounting an effective counterattack.14 The Coastwatchers were so well positioned to observe Japanese ship movements and air raids toward Guadalcanal that their intelligence enabled the Allied naval forces to rarely be caught off guard. Regarding Japanese attacks against Guadalcanal in 1943, “the Coastwatchers were placed to check on the entire sequence of movements.”15 Because of this fidelity, Allied ships and aircraft were able to repeatedly outmatch the Japanese attacks. The reporting of these threats communicated a multi-domain intelligence picture to the naval fleet.

This image from the Reports of General MacArthur depicts the air and sea line of communication known as the “slot” that served as the main avenue of approach for Japanese counterattack during the Solomon Islands Campaign. The location of Coastwatcher stations along this main avenue of approach decreased uncertainty for the naval force as Japanese forces counterattacked.16 (Library of Congress)

Naval intelligence must be multi-domain just as the single naval battle addresses the multi-domain operating environment. The single naval battle seeks to, “link the elements of naval power projection into a seamless web of integrated capabilities across air, maritime (surface and subsurface), land, space, cyber and cognitive domains.”17 The Coastwatchers collected intelligence from the sea, air, and land, and so must modern naval forces. Furthermore, new technologies now enable navies to collect intelligence from new domains and old domains in new ways. The space and cyberspace domains were not available to the Coastwatchers, but are becoming increasingly important today. The number of satellites in orbit is expected to increase five times in the next ten years.18 In the cyber domain, CISCO forecasts that the number of networked devices globally will be three times that of the number of humans on earth by 2023.19 Analyzing threats through multiple domains is imperative in preparation for the future single naval battle. Naval intelligence collection must occur in all domains to prepare for these threats.

The Coastwatchers capitalized on access to the archipelagos of the South Pacific and the knowledge of individuals who were familiar with the environment. The Coastwatcher organizations were comprised of islanders, settlers of European descent, who knew how to survive on these islands and were familiar with the natives. The title of islander was earned once a settler had spent four or five years living on one of the islands, ensuring their knowledge of the environment. These islanders had various occupations such as administrative officers, miners, prospectors, missionaries, planters, or patrol officers.20 Additionally, island natives were an essential part of the Coastwatcher networks. They provided assistance that was not otherwise available by serving as scouts, spies, couriers, radio operators, medics, porters, and navigators.21 Natives also provided force protection from Japanese patrols. Some natives had an unwavering commitment to the Coastwatchers effort, while others allied with the Japanese as they began occupying islands. The allegiance of the natives often determined the success of the Coastwatchers on a particular island. Commander Eric Feldt stated, “There was no possibility of any European posing as a native. Concealment was our only hope and this meant mobility… In other countries, however, it might be very different and the best concealment might be in the slums of a large city. Anywhere, the natives of the country will be the best operators.”22 The Coastwatchers were fortunate to have had access and local support in these island locations, but the end of colonial empires makes access and local support much less certain in the present day.

Access and local support are essential to effective intelligence during the single naval battle. The proactive multi-domain intelligence operations of the single naval battle require diplomatic partnerships and agreements to provide placement and access. Furthermore, host nation or local support is important for the variety of tasks and knowledge that only natives can provide in maintaining such a network. Proactive naval intelligence requires access and support from partners and allies.

The historic success of the Coastwatchers provides valuable insight for naval intelligence in the future single naval battle. Proactive intelligence, multi-domain intelligence, and local access and support remain necessary for an effective naval intelligence operation. Naval forces will grow stronger through these lessons as the world’s security environment becomes more complex and dynamic. The future challenge is to harmonize these lessons into a single integrated naval force. As the naval force tackles this and other challenges, remember the Coastwatchers.

Captain Michael Van Liew is a United States Marine Corps Intelligence Officer who, at the time of original publication, was assigned as a student at Expeditionary Warfare School in Quantico, VA.


1. Amphibious Capabilities Working Group, Naval Amphibious Capability in the 21st Century: Strategic Opportunity and a Vision for Change (Washington, DC: United States Marine Corps, April 27, 2012), 4,

2. Amphibious Capabilities Working Group, 33.

3. Eric A. Feldt, The Coastwatchers (Coppell, TX: The War Vault, 2019), 12.

4. Feldt, The Coastwatchers, 7.

5. David Oswald William Hall, The Official History of New Zealand in the Second World War 1939-1945: Coastwatchers Episodes and Studies Volume 2 (Wellington, NZ: War History Branch of the Department of Internal Affairs, 1951), 4 and 28–29,; Justin Haynes, “Human Intelligence as a Deep Sensor in Multi-Domain Operations: Australia’s World War II Coastwatchers,” Military Intelligence Professional Bulletin 45, no. 3 (July-September 2019), 35, Features/HumanIntelligenceasaDeepSensorinMulti-DomainOperations.pdf.

6. Sources used to create this depiction include Central Intelligence Agency, Oceania, map, in The World Factbook (Washington, DC: Central Intelligence Agency, March 4, 2021),; Hall, 4–5 and 28–29; Feldt, The Coastwatchers, 8, 12, and 138–143; John Brown, “Coast Watchers in the Solomons,” Warfare History Network, last modified August 29, 2016,; Madison Pine and Geraldine Warren, “Our Coastwatchers,” Auckland War Memorial Museum, last modified August 11, 2020,

7. Peter Djokovic, “The Coastwatchers and Ferdinand the Bull,” Semaphore 4 (2014), 2,

8. Feldt, The Coastwatchers, 8; Hall, 3.

9. Eric A. Feldt, “Coastwatching in World War II,” Proceedings 87, no. 9 (September 1961), 72,

10.  Feldt, The Coastwatchers, 9.

11.  Amphibious Capabilities Working Group, 5.

12. Amphibious Capabilities Working Group, 5.

13.  Haynes, 34 and 38.

14. James D. Hornfischer, Neptune’s Inferno: The U.S. Navy at Guadalcanal (New York: Bantam Books, 2011), 4–5, 124.

15. Feldt, The Coastwatchers, 85, 102.

16. Douglas MacArthur’s General Headquarters Staff, Reports of General MacArthur: The Campaigns of MacArthur in the Pacific (1994, Washington, DC: Library of Congress, 2006), 81-84,

17. Amphibious Capabilities Working Group, 5.

18. Konstantin Kakaes, Tate Ryan-Mosely, and Erin Winnick, “The Number of Satellites Orbiting Earth Could Quintuple in the Next Decade,” MIT Technology Review, June 26, 2019,

19. Kelly Hill, “Connected devices will be 3x the global population by 2023, Cisco says,” RCR Wireless News, February 18, 2020,’s%20new%20annual%20forecast%20predicts,Internet%20Report%20analysis%20and%20forecast.

20.  Feldt, The Coastwatchers, 27–31.

21. Anna Annie Kwai, Solomon Islanders in World War II: An Indigenous Perspective, State, Society and Governance in Melanesia Series (Acton, ACT, Australia: Australian National University Press, 2017), 3, 17-19, 22, 27, 29, 37–40, and 43–44,

22. Feldt, “Coastwatching in World War II,” 75.

Featured Image: A local wireless telegraphist operator operating an AWA 3BZ teleradio at Segi Coastwatchers station, British Solomon Islands. (Photo courtesy of the Australian War Museum)

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