The grinding Ukrainian military offensive during the summer of 2023 has been a frightful sight for undersized nations fashioning their own defensive strategies against Russia or China. Small nations invaded by numerically superior foes simply do not have the combat power to win a combined arms fight. To nullify this overmatch, out-gunned states require asymmetric options to deter and defend. If deterrence falters and the defense cracks, there are few options to prevent enemy consolidation of control. One irregular option, increasingly present in small-nation defense plans, is the so-called “stay-behind force.”
The purpose of a stay-behind force is plainly stated in the name: pre-designated operatives who plan to hide, survive, and eventually operate in the rear area of an advancing enemy. Stay-behind forces can slow advances, buy time, impose costs, create confusion, and psychologically demoralize an invading enemy. In military terms, this is a delaying action, not a defeat mechanism. Stay-behind forces are typically, but not always, a commando-type organization operating clandestinely.
Investing in stay-behind forces is on the rise but remains contentious. The very concept presumes failure. Building a stay-behind force implies that a state will not be able to stop an invader at its borders, and further acknowledges that counterattacks might not expel the occupier. Investing in stay-behind forces, however prudent, signals that occupation is possible or probable — a proposition that nations can be reluctant to admit. Even so, NATO countries in Eastern Europe such as Estonia, Latvia, Lithuania, and Poland, as well as non-aligned countries such as Georgia and Taiwan, are formulating new national defense and whole-of-society resistance strategies. All face a vastly superior adversary. None can afford force parity. All are considering, or already have, a stay-behind force concept.
This article provides a framework for stay-behind force decision-making, addressing the single decision that is seldom tested in wargames and is difficult to replicate in training scenarios: when a stay-behind force should remain and fight or flee and evade. After defining types of stay-behind forces, four “occupation” environments are described, differentiated by occupier methods. The four environments are: decapitation, pacification, subjugation, and liberation. This framework is designed to aid a resistance leader or stay-behind force advisor in making the decision: Should I stay, or should I go?
Types of Stay-Behind Forces
Stay-behind forces fall into two general categories. The first are specialized military units such as long-range reconnaissance teams that stay behind to provide intelligence and assist in target acquisition. These units are small, hit-and-run elements that free range in occupied areas and create havoc in the enemy’s rear area. The British Special Air Service operations in North Africa in 1942 against Erwin Rommel’s Afrika Korps offer one famous example. In the Cold War, this category included deep-strike teams designed to service strategic targets inside enemy occupied area via raids, sabotage, or demolitions. Often, these were not intended to be unilateral operations. They were designed to aid or operate with indigenous, partisan units.
The military unit in which I spent a decade serving, the 10th Special Forces Group (Airborne), is one such unit. The 10th Group was assembled in 1952 and rushed to West Germany to serve in a stay-behind role. The special forces teams were to remain behind the lines after a Soviet Union invasion of central Europe. The mission was to organize and operate resistance networks of partisans that would impose costs on Soviet rear echelons. The classified plans, which were artifacts of the Cold War by the time I read them in 1997, were never activated. Were these 12-man special forces teams truly ready to execute this mission? We do not know. These ideas and organizations were untested.
The second organization — or collective of organizations — is the shadowy, pre-prepared clandestine network, run by intelligence organizations, that organizes citizen resistance. These networks furnish intelligence, circulate propaganda, or take part in direct actions such as subversion and sabotage. The World War II French resistance units typify this approach, with one fatal caveat: They were not pre-conceived. French resistance cells were scrambling start-ups that took shape after the capitulation of France on June 17, 1940. Despite their gutsy heroism, the French Resistance units only organized themselves well after the fall of France. Geographically distributed, ideologically distinct, and wholly uncoordinated, the French resistance groups never seriously challenged the occupying German forces. German consolidation was total and complete, six weeks after the invasion.
Four Occupation Environments
As a Joint Special Operations University adjunct who teaches these concepts and strategies, I have observed that investment in stay-behind forces is a gambit with decision-making peculiarities that lie outside of most doctrinal frameworks. In this context, classifying occupation environments into four categories can help inform the decision to “stay or go.”
No matter how a state builds its stay-behind forces or intends for them to be employed, it is the occupation environment that truly dictates decision-making. The stay-behind force is not designed to engage in a contest of wills or act in accordance with a doctrinal template. It is a counterpuncher and a shapeshifter, intended to attack a narrow range of vulnerabilities revealed by the occupying power. Thus, it is the occupation force’s behaviors more than the stay-behind force itself that dictates actions. The occupation environment includes the forces, methods, and repressive measures that an occupier uses to control territory, resources, infrastructure, and people.
Decapitation
The first scenario in which a stay-behind force can remain is when the invader pursues a decapitation strategy with a modest military occupation to follow. The invader presupposes that the existing security apparatus can be cowed, coerced, or rapidly refashioned into accepting a new regime with minimal upheaval. The invader assumes that current structures, behaviors, and organizations can remain in place, obviating the need for costly occupying forces. To be sure, portions of the population will be displaced, deported, or prosecuted, but the superstructure of security forces will not change drastically.
In this environment, potential stay-behind forces can monitor transitions like shifts and factionalism within security forces. Stay-behind forces can then make an analytic assessment of their political alignment and survivability. Borrowing from revolutionary insurgent groups, stay-behind operatives can judge if the moment is suited for low-signature acts such as organizing, planning, and posturing, or if the chaotic moment is more ideal for aggressive actions that can stymie consolidation of control.
Decapitation strategies are attractive to imperial states based on the promise of quick victory, limited casualties, and a low-cost war. The U.S. invasion of Panama in 1989 sought to expel Panamanian leader Manual Noriega and “swap the leadership” while keeping the security apparatus largely intact. The Soviet invasion of Afghanistan in 1979 was also a decapitation operation. The Soviet Union overthrew the Afghanistan government with a coup de main commando raid backed by a relatively light invading force of 30,000 troops. In these types of invasions (and occupations), disciplined stay-behind forces stand a reasonable chance of evading and operating. Unless they elevate themselves on the occupier’s target list by conducting splashy operations or media campaigns, stay-behind forces should remain behind as cohesive units of action.
Pacification
The second potential condition in which stay-behind groups can successfully remain is when the invading force intends to mollify or pacify the population — not dominate and terrorize. This type of occupier limits the violence that they will inflict, either by virtue of their ethics or the belief that excessive violence will be counterproductive.
This model approximates the U.S. military approach in Iraq in 2003, whereby the defeat of the Iraqi army was (falsely) expected to secure the compliance of the Iraqi population. When the Iraqi population began to self-organize against the U.S. occupying force, the United States limited its use of force while banking on new Iraqi governance as the antidote. Once the Iraqi population mapped the methods of the coalition occupation, select Iraqis judged that they could recruit, assemble, and fight the coalition and the embryonic Iraqi security forces. The Iraqi wait-and-see types soon formed into — or joined — resistance movements. By late 2004, the U.S.-led coalition (in which I served as a special forces officer), lost the initiative. Seven years later in 2011, U.S. forces departed Iraq, a superpower in retreat.
This type of occupation environment favors stay-behind forces in that they can rapidly identify the narrow range of behaviors (acts of terror, violence, subversion) that draw the attention of occupation forces. This operating space allows for the contemplation of a suitable stay-behind strategy, plan, and method.
Subjugation
The third occupation type is subjugation. This is a brutal scenario, but one where stay-behind forces can still successfully organize, despite violent and repressive measures.
In World War II Poland, the occupying Germans sought to impress large portions of the Polish population into a long-term work force. The Poles who were not killed or starved were enslaved as captured labor. Thus, the German regime sought to extract the fruits of Polish labor to bolster the German industrial war effort. This occupation method allowed room for the growth of the “Polish Underground State,” complete with a sophisticated, stay-behind, armed component.
The Polish Underground State organizational model informed the current U.S. Army Special Forces doctrine on resistance. This U.S. doctrine, in turn, informed the Resistance Operating Concept, the manual that has stimulated stay-behind force designs in Eastern Europe and around the Black Sea. In this model, a resistance has four components: an underground, the brain and nervous system of the resistance; an auxiliary of supporters and citizens who provide supporting functions; an armed element consisting of guerrilla forces; and a public component, the political face and voice of the movement.
In 2023, occupied portions of Ukraine resemble a subjugation occupation, even if the Russian Federation is not conducting (and cannot conduct) a wholesale impressment of Ukrainians in occupied territories like Germany did in Poland. At the tactical level, this helps the Russian occupiers. They do not need to provide for the welfare or sustain the productivity of captured citizens and there are few limits on the methods used to repress and control. The longer the war continues, the more the occupying force devolves into a criminalistic and sadistic enterprise. This creates grim conditions for operations behind enemy lines. In these situations, the best option for stay-behind forces is to flee and operate from a safe haven or shift operations to more permissive areas.
Liberation
The fourth condition favorable for a “stay” decision is where stay-behind forces have some expectation that a liberating force is coming and they can stay without being detained, deported, or killed. In occupied France in 1944, allied supporters such as the U.S. Jedburgh teams, paired with French resistance units, provided intelligence and created delaying actions to aid in Operation Overlord, the allied invasion of France. In this case, the “stay or go” decision was made on the perceived timing and presumed arrival of the liberating force.
Conclusion
Despite their name, stay-behind forces should always be prepared to flee an invading force. In the face of an invading enemy with the intent to occupy and control, staying behind might be a poor tactical choice at best and a suicidal act at worst. Stay-behind forces must survive to contribute. Unless a stay-behind force has a realistic environment in which to survive and operate, they should be prepared to flee and fight another day and in another way. Modern surveillance and detection technologies have made it difficult for stay-behind forces to hide, congregate, and operate. The digital signature is a tactical problem that plagues modern stay-behind concepts. This is one reason why investing in stay-behind forces is a gambit. Realistic employment options are somewhat unknowable prior to actual occupation.
The U.S. military has a strong interest in aiding allies and partners in building stay-behind forces. Friendly nations’ stay-behind forces, if capably conceived and legitimized by the state, are ideal partners for U.S. special operations forces. Unconventional warfare, a core mission of U.S. Special Operations Command, is conducted by partnering with local, irregular forces in contested or occupied areas. Such irregular forces, typically outgunned and outnumbered by the occupier, fight on borrowed time. These groups require external support to fight, survive, and win. In recent decades, the U.S. conducted successful unconventional warfare campaigns with Afghanistan’s Northern Alliance in 2001, with the Iraqi Kurds in 2003, and with Syrian Democratic Forces beginning in 2014. For countries facing Russian aggression or Chinese encroachment, the matching of stay-behind forces with U.S. special operations provides a clear asymmetric advantage. If done before a crisis, visibly and credibly, it also produces a deterrent effect.
Crafting a stay-behind force strategy should start by juxtaposing the utility of the stay-behind force against the expected (or actual) occupation environment. Decision-makers should understand the contextual environment before deciding on employment options. The four occupation environments described above can inform the decision-making of leaders and resistance units.
Brian Petit, a retired U.S. Army colonel, teaches and consults on strategy, planning, special operations, and resistance. He is an adjunct for the Joint Special Operations University and a 2023 non-resident fellow with the Irregular Warfare Initiative, a joint production of Princeton’s Empirical Studies of Conflict Project and the Modern War Institute at West Point.
Image: National Archives and Record Administration
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