The undersea fight will be so critical in the High North and in the western Pacific that the Marine Corps must be part of it.
– Commandant General David H. Berger
I don't mean to be dramatic, but I feel like, if the Navy loses its head, if we go off course and we take our eyes off those things we need to focus on . . . I think we may not be able to recover in this century.
– Chief of Naval Operations, Admiral Michael Gilday
I suspect that, at best, the Pentagon’s budgets will start flattening out . . . There's a reasonable prospect that they could actually decline significantly.
– Chairman of the Joint Chiefs of Staff, General Mark Milley
U.S. military leaders have clearly articulated the near-term challenge posed by our main strategic competitors, China and Russia, alongside the stark reality that increased near-term defense spending will not be a viable option to meet that challenge. Both potential adversaries are investing heavily in their respective submarine forces, requiring a significant refocus on Navy antisubmarine warfare (ASW) capabilities.1 To meet this growing threat without relying on increased funding, the Navy will have to improve its operational employment of assets already at-hand instead of gambling on unproven and theoretical future forces.
The Navy can find inspiration from its past. The “Cactus Air Force” was thrown together at Henderson Field during the 1942 Battle for Guadalcanal. Disparate Marine Corps, Navy, Army Air Corps, and Royal New Zealand Air Force units melded together on the fly to form the key operational unit in a struggle that turned the tide of World War II in the Pacific. Notably, their main operating base resembled many of the aspects now incorporated in the modern expeditionary advanced base operations (EABO) doctrine in development by the Marine Corps.2 Just as Navy and Marine Corps forebears maximized the capabilities of F4F-4 Wildcats, SBD-3 Dauntless dive bombers, P-400 Airacobras, and B-17 Flying Fortresses in the dark days of early–World War II, a modern naval force could form “Cactus21”—air combat elements (ACEs) comprised of MH-60R Seahawks, MH-60S Knighthawks, MQ-8C Fire Scouts, and MV-22B Ospreys.
Only one of these aircraft, the MH-60R, is currently used in an ASW role. However, the MQ-8C and MH-60S could join the ASW fight and significantly boost both the quantity and quality of the Navy’s ASW operational units with minimal investments, potentially offset by divestments of legacy capabilities. The Cactus21 ACE’s capabilities would fall neatly in-step with two burgeoning doctrinal and capability developments: the Chief of Naval Operations’ drive to build a robust naval operational architecture with Project Overmatch and the joint Navy–Marine Corps’ focus on potential EABO and littoral operations in a contested environment (LOCE) meant to control key “maritime terrain.”3
In traditional ASW operations, aircraft custom-built to track and target submarines launch from the same ships they are meant to protect and then play “defense” with a layered protection scheme around friendly units. The Cactus21 ACE could launch from shore bases and littoral vessels and execute “offensive” ASW in pre-selected chokepoints, far in advance of the main naval force. Just as Marine Corps and Navy tactical aircraft destroyed threat warships advancing south from the Japanese base at Rabaul, the Cactus21 ACEs could form lethal ASW barriers in potential future conflicts against Chinese or Russian submarines in strategically relevant areas.
General Berger detailed the fundamental Marine contribution to that future ASW fight, “(through) forward logistics and support, as well as sensor and strike capabilities, Marine expeditionary advanced bases (EABs) could make a significant contribution to undersea warfare campaigns, including holding Chinese and Russian submarines at risk.” The Cactus21 ACE would constitute the preponderance of that ASW sensor capability and its entire ASW strike capability in the form of air-dropped Mark 46/54 Lightweight Torpedoes (LWTs). Captain and Commander Ilteris subsequently highlighted in their Proceedings article, “Resurrect the Hunter-Killer Group,” additional sea-basing options onboard LPDs and LHA/Ds, which they named “21st-century hunter-killer groups (HUK21).” The MH-60Rs, MH-60Ss, MQ-8Cs, and MV-22Bs constituting a Cactus21 ACE could easily transition between shallow water ASW from EABs and littoral combat ships (LCSs) to blue water ASW in the HUK21 construct, according to the developing operational situation.
The April 2021 Proceedings article, “Implementing Expeditionary ASW,” pushed the concept even further and highlighted a fundamental challenge to traditional ASW operations: they require “large numbers of ships and aircraft to counter each enemy submarine.” Using the United Kingdom’s ASW efforts during the Falklands War against Argentina as a reference, the article articulated the modern threat: “Argentine forces possessed the potential to derail the entire British Falklands campaign with a single submarine. What effects would 76 Chinese submarines have in a great power conflict?” According to the authors, the answer to this challenge partially rests on developing new platforms including long-range unmanned surface vessels (LRUSVs), new lightweight torpedoes called compact rapid attack weapons (CRAWs), and ASW ordnance for HiMARS-fired Guided Multiple Launch Rocket System (GMLRS). Unfortunately, these solutions suffer from two significant drawbacks: the immature technology may not reach the fleet in time to meet the threat and our expected flat or declining future defense budgets will make it difficult to buy new capabilities. According to the former Indo-Pacom Commander, Admiral Phil Davidson, great power competition could turn violent in this decade. Thus, the Navy needs ready and reliable tools at hand sooner rather than later.
The Cactus21 ACE Operating Environment
The recent Tentative Manual for Expeditionary Advanced Base Operations defined EABs as, “a locality within a potential adversary’s weapon engagement zone (WEZ) that provides sufficient maneuver room to accomplish assigned missions seaward while also enabling sustainment and defense of friendly forces therein. Its expeditionary nature means it is not permanent and must be able to change location quickly enough to maintain relative advantage.”4 The temporary and low-signature characteristics of EABs make rotary wing platforms ideal aviation assets to operate within the EABO construct. Runways and support architecture required by fixed-wing aircraft such as the P-8 and MQ-4 are easily targetable by the enemy. They should therefore operate from bases outside the enemy’s WEZ and transit to and from the Cactus21 ACE’s area of responsibility. This transit time, along with the expected scarcity of maritime patrol reconnaissance aircraft (MPRA), mean EABO ASW assets will need to provide their own persistent-sensor coverage from austere EABs ashore or helicopter-capable supporting vessels concealed in the littoral environment.Picture EABO/LOCE airfields as converted soccer pitches and vessels with a single helicopter landing spot, not local airports or established military bases. This is the exact environment in which Navy and Marine Corps rotary wing units thrive, as evidenced by countless hurricane relief efforts and decades of deployments on board small combatants.
The Tools at Hand
The MH-60R Seahawk is the preeminent ASW helicopter in the world and would play a huge role in a Cactus21 ACE. Equipped with sonobuoys, torpedoes, surface-search radar, ESM, and an electro-optical sensor, their expert ASW crews can detect, localize, classify, and attack any submarine on the planet. Seahawks have proven their value to such an extent that six allied and friendly navies have added them to their fleets. The helicopter maritime strike (HSM) community has decades of sub-hunting experience, and its aircrews would likely lead most ASW campaigns based on that expertise. However, carrying this much capability does have one large drawback: weight. A fully fueled MH-60R with a complete ASW sensor suite is typically limited to carrying just one lightweight torpedo. Also, a major conflict against China or Russia would likely drive the deployment of every available surface combatant, many of which will require embarked MH-60R support. Largely because of the platform’s proven utility in the ASW fight, they would quickly become a scarce asset in any future conflict against a peer adversary.
Focused on antisurface warfare, logistics, rescue, and airborne mine-countermeasures missions, the MH-60S Knighthawk is not currently configured to conduct ASW missions. However, with a minimal investment, the Knighthawk could be modified to carry two lightweight torpedoes. Since sonobuoys can be hand-launched from airborne helicopters, Knighthawks could also seed large buoy fields and leave their monitoring to another platform. With the network capability from Project Overmatch, they would not need their own ASW sensors to obtain valid targeting solutions—other platforms would find the targets and the MH-60S “torp truck” would kill them. Including the Knighthawk in the Cactus21 ACE construct would also roughly double the available rotary wing assets and compensate for the scarcity of Seahawks outside of the carrier strike group construct. Finally, EABs and littoral vessels will have significant logistics and force protection requirements to support their offensive operations. The MH-60S excels as a medium-lift cargo transport as well as a close-air support asset and could serve as the “jack of all trades” in the EABO/LOCE construct.
The MQ-8C Fire Scout unmanned aerial vehicle (UAV) also currently suffers from a lack of ASW sensors, but that is likely to change in the near future.5 Testing indicates that an airborne Fire Scout, with a mission endurance two to three times greater than the MH-60R, could monitor huge sonobuoy fields with the minor investment of adding a sonobuoy processor to the aircraft.6 The Fire Scout could operate from an EAB or LCS and provide “persistent stare” at likely strategic choke points astride the key maritime terrain. Fully networked with their partner forces, they would likely be the first platform to detect enemy submarines and pass the contacts for prosecution and attack. Importantly, this long-dwell monitoring of ASW sensors would compensate for the reduced role P-8 aircraft would play in the EABO/LOCE construct because of the range and potential enemy surface-to-air threats.
Marine MV-22B or Navy CMV-22B Osprey tiltrotor aircraft would also be an important member of a Cactus21 ACE. They already excel in long-range logistics support and would likely serve as a primary supply link between EABs and supporting “sea bases”—amphibious support ships operating at sea and outside the enemy’s WEZ.7 Besides delivering fresh supplies to forward positions for others to employ, Ospreys could also hand-launch large sonobuoy fields in a similar fashion to the Knighthawks. Once again, within Project Overmatch’s resilient network, different platforms could deploy and exploit a variety of passive and active sensors to form a link in the kill chain, allowing the Osprey to meet the Commandant’s guidance for Marines to join the ASW fight.
Once established as an operating construct, Cactus21 ACEs would easily incorporate additional airborne and surface assets. As already detailed, P-8s could transit to the operating area to join ASW efforts in the littorals. Coalition ASW assets could also join the Cactus21 ACE in a similar fashion to the Royal New Zealand Air Corps’ place in the original Cactus Air Force. MH-60R support from partner navies would be especially useful. “Non-traditional” ASW vessels, such as the Spearhead-class fast transport vessels and almost any other ship with a flight deck, could add to the distributed nature of the force. Finally, even much-maligned Freedom- and Independence-variant littoral combat ships could provide important support to the ASW effort without waiting for their delayed ASW mission package. To support the Cactus21 ACE, vessels would have to fit at least one MH-60, provide berthing and maintenance facilities for aircrew and support personnel, and supply the fuel and ordnance needed for ASW operations—a relatively low standard that both types of LCS vessels can meet today.
The original Cactus Air Force was built from scratch on Henderson Field in 1942 to defend Guadalcanal from a Japanese advance. While the Marine Corps, Navy, and allied units may have been surprised to fly and fight together, naval planners in the pre-war period laid the foundations for their success with a focus on the threat posed by a growing potential adversary. The Navy–Marine Corps team now finds itself in a similar period, with peer competitors and predictable operating environments. The EABO and LOCE concepts are important efforts to meet tomorrow’s challenge with deliberate planning for a potential future conflict. Adding Cactus21 ACE capabilities to those plans will use the tools already at hand to help deter and defeat the nation’s enemies in the next war.
- Congressional Research Service, “China Naval Modernization: Implications for U.S. Navy Capabilities—Background and Issues for Congress,” 9 March 2021; “Russian Armed Forces- Capabilities,” 30 June 2020.
- Department of the Navy, Headquarters, United States Marine Corps, “Tentative Manual for Expeditionary Advanced Base Operations,” February 2021.
- Chief of Naval Operations Memorandum to Rear Admiral Douglas W. Small, Subject: PROJECT OVERMATCH, 1 Oct 2020.
- Department of the Navy, Headquarters, “Tentative Manual for Expeditionary Advanced Base Operations,” 1–6.
- Sam LaGrone, “Northrop Grumman Pitching Fire Scout Helicopter Drone for ASW Missions,” USNI News, 16 February 2021; Michael Peck, “Navy Wants to Turn Fire Scout into Sub Hunter,” C4ISR Online, 19 February 2015.
- Thomas Twomey, “Fire Scout Unmanned Air System Anti-Submarine Warfare (ASW) Technologies (Informational Brief),” Northrop Grumman, 2 October 2015.
- Department of the Navy, “Tentative Manual for Expeditionary Advanced Base Operations,” 1–6.