The Role of Stand-in Forces in Maritime COIN

If the U.S. government and its partners wish to pursue a maritime counterinsurgency (COIN) strategy, two questions need to be answered: What sort of military force would the U.S. need? And, how would those forces be positioned to succeed? The Marine Corps’ Concept for Stand-in Forces offers an answer: stand-in forces (SIF) arrayed in an active, integrated maritime defense-in-depth (AIMD2).

An effective maritime COIN strategy demands a force posture that provides a sustainable, persistent, dynamic, and physical presence to deter insurgent activities and reassure local forces and populations. Some may suggest that “virtual presence,” enabled by emerging technologies, is just as effective as physical presence. But with insurgents physically present to threaten, harass, intimidate, and coerce civilian compliance with Beijing’s will, allies and partners reasonably consider U.S. virtual presence to be actual absence. The SIF concept provides details for a force posture well-suited to address this challenge. It is important to note that while this concept is rightly focused on the Indo-Pacific region, its principles are universal and scalable—even for “economy-of-force” theaters.¹

Why Stand-in Forces?

SIF are the latest idea in a continuing evolution of thinking and its associated family of future naval operating concepts. Littoral Operations in a Contested Environment (LOCE), published in 2017, defines naval/maritime integration in detail and explains why it is essential given current and emerging threats. The Navy’s Distributed Maritime Operations, published in January 2019, outlines the logic of distributing the fleet to enhance lethality and resilience. Expeditionary Advanced Base Operations (EABO), published in March 2019, applies the thoughts and lessons of LOCE in operational and tactical contexts. And the SIF concept, first put forward in The 38th Commandant’s Planning Guidance (2019), then developed in December 2021, describes the Commandant’s vision for maritime defense in depth.

SIF are “small but lethal, low signature, mobile, relatively simple to maintain and sustain forces designed to operate across the competition continuum within a contested area as the leading edge of a maritime defense-in-depth to intentionally disrupt the plans of a potential or actual adversary.”² Stand-in forces may comprise combinations drawn from the Marine Corps, Navy, Coast Guard, special operations forces, interagency, and allies and partners. Although U.S. forces regularly operate within potentially contested areas, SIF are optimized to persist in those areas during conflict while also maintaining an ongoing competitive presence that fosters strong relationships with regional allies and partners; develops and maintains maritime domain awareness; and gathers intelligence, counters malign behavior, and deters conflict.

Conducting the enduring tasks of reconnaissance and counterreconnaissance enables SIF to gain and maintain contact with adversaries below the threshold of conflict. If conflict does occur, SIF’s adversary contact information can easily become targeting data for fleet and joint forces. Conversely, its maritime domain understanding will help prevent adversaries from sensing and targeting those same fleet and joint forces.³

As conceived, stand-in forces are a modern, maritime version of a previous, successful COIN force: the Marine Corps’ Vietnam-era Combined Action Platoon (CAP) program.⁴ The similarities between SIF and CAP are striking: Both aim to restore respect and credibility of the rule of law; emphasize maintaining contact with the adversary; place U.S. forces forward to live with and around local forces and populations; empower allies and partners by complementing their capabilities to counter adversary malign behaviors; and help local forces defend the integrity of their own sovereign territory. Should matters escalate from the day-to-day status quo into higher-end conflict, both position forces to help defend that sovereign territory and facilitate the introduction of reinforcements to defeat aggression against U.S., allied, and partner interests.

Despite the demonstrated operational success of CAP’s clear-and-hold approach within the Marines’ operating area, its notable popularity with local civilian populations, and supporting statistics, senior U.S. military leaders refused to abandon their more traditional attrition-based search-and-destroy approach until it was too late to influence the outcome of the war in Vietnam.⁵

How SIF Could Execute Maritime COIN

A force tasked to undertake maritime counterinsurgency in the South China Sea or elsewhere must be able to accomplish four essential goals to defeat the insurgency short of war or prevail against enemy conventional forces in the event of kinetic escalation. First, it must seek and support efforts that incentivize compliance with the provisions of the U.N. Convention on the Law of the Sea. Second, it must deter escalation to armed conflict while responding to harassment or punishment of U.S. regional allies and partners. Third, it must empower those allies and partners to defend and exercise their own territorial sovereignty. Last, if deterrence fails and the situation escalates, it must facilitate the introduction and employment of additional forces and capabilities to help defend U.S. friends and allies against aggression. This is precisely what SIF are designed to accomplish, and the AIMD2 effectively positions SIF to succeed:

The most forward elements that are first to gain contact with the potential adversary will typically be unmanned. Next will be a manned and unmanned area characterized by teaming. Its purpose will be to control the forward elements, operate an additional layer of manned and unmanned sensors, integrate operations with allies and partners, and to provide direction and support to unmanned systems as they cycle forward.⁶

Keep in mind that SIF are considered the leading edge of an integrated defense in depth. The first two layers (the unmanned and the manned-unmanned teaming) emphasize winning the reconnaissance and counterreconnaissance competition; gaining and maintaining contact with the insurgents; empowering allies and partners to defend their exclusive economic zones and key maritime terrain; and responding to bad behavior. SIF allow the United States to maintain a dynamic, resilient presence that disrupts adversary plans and complicates insurgency activities. The platforms in these layers should also feature modular payloads with both lethal and intermediate (that is, nonlethal) force capabilities to further complicate the insurgents’ decision-making calculus. The Concept for Stand-in Forces adds: “An additional layer will host major weapon systems, required logistic support, and additional command and control elements (and possibly forward arming and refueling points, if required).”⁷

The third layer of the AIMD2, the expeditionary advanced base (EAB), supports the two forward layer, including additional fires and weapon systems, sustainment (e.g., fuel/power/energy, maintenance, subsistence, etc.), and additional command and control. EABs not only sustain but also connect SIF to major fleet and joint force elements residing outside the contested area:

Anything requiring significant sustainment or manpower support will ideally be postured afloat and/or ashore outside the contested area to minimize the footprint and signature inside the contested area. This concept envisions long-duration and long-range unmanned systems bedding down outside the contested area to the maximum extent possible.⁸

The fourth layer, composed of large, standoff, legacy forces outside the weapons engagement zone, provides critical depth to the defensive posture, designed to back up the three advanced layers by surging forward at opportune times and places to mitigate adversary sea-denial capabilities and, if required, bring decisive combat power on target.

China’s maritime insurgency harmonizes proven insurgency methods with modern capabilities to challenge the international order at sea. The U.S. government and its regional partners must harmonize proven COIN strategies with modern military capabilities to defend and maintain the accepted international order. SIF, as part of the AIMD2 structure, provide the necessary, credible military force as part of a comprehensive maritime COIN strategy.