In a stay-behind operation, a country places secret operatives or organisations in its own territory, for use in the event that an enemy occupy that territory. If this occurs, the operatives would then form the basis of a resistance movement or act as spies from behind enemy lines. Small-scale operations may cover discrete areas, but larger stay-behind operations envisage reacting to the conquest of entire countries.
Stay-behind operations of significant size existed during World War II. The United Kingdom put in place the Auxiliary Units. Partisans in Axis-occupied Soviet territory in the early 1940s operated with a stay-behind element.
During the Cold War, the North Atlantic Treaty Organisation (NATO) and the Central Intelligence Agency (CIA) sponsored stay-behind networks in many European countries, intending to activate them in the event of that country being taken over by the Warsaw Pact or if a communist party came to power in a democratic election. According to Martin Packard they were "financed, armed, and trained in covert resistance activities, including assassination, political provocation and disinformation."
Many hidden weapons caches were found in Italy, Austria, Germany, the Netherlands and other countries, at the disposition of these "secret armies". The most famous of these NATO operations was Operation Gladio, acknowledged by Italian Prime Minister Giulio Andreotti on October 24, 1990.
List of known stay-behind plans
- Auxiliary Units (United Kingdom)
- Attack on the WSA (Luxembourg)
- O&I (Netherlands) (The Dutch secret stay-behind organisation was the only non connected NATO organisation in Europe.)
- Operation Gladio (based in Italy, active in many countries)
- Aginter Press (Portugal)
- Lochos Oreinon Katadromon, or LOK (Greece)
- Operation (Red) Sheepskin (Greece)
- Austrian Association of Hiking, Sports and Society (OeWSGV, also: ÖWSGV) (Austria)
- Plan Bleu, La Rose des Vents, and Arc-en-ciel (France)
- ROC (Norway)
- SDRA8 and STC/Mob (Belgium)
- Bund Deutscher Jugend – Technischer Dienst, or TD BJD (Germany-West)
- KgU - Kampfgruppe gegen Unmenschlichkeit e.V. (A secret stay-behind organisation of West-Berlin against the GDR 1948-1959 with strong Support of CIA)
- Özel Harp Dairesi (Turkey)
- Nihtilä-Haahti plan (Finland)
- Projekt-26 (P-26, Switzerland)
- Werwolf (Nazi Germany)
- Regional Force Surveillance Units (Australia), non-secret units of the Royal Australian Corps of Infantry with officially acknowledged 'stay-behind' duties.
- Arla gryning and Informationsbyrån ('IB') in Sweden.
- Operation Tracer (Gibraltar)
- Clandestine cell system
- False flag
- Japanese holdout
- Long-range reconnaissance patrol
- Partisan militia
- Collins, John M. (1998). Military Geography. Potomac Books, Inc. p. 122. ISBN 9781597973595. Retrieved 2013-09-28.
The Pripet Swamp, which created a great gap between German Army Group Center and Army Group North soon after ... June 1941, made it impossible for large military formations to conduct mutually supporting operations. Attempts to bypass such extensive wetlands proved perilous, because outflanked Soviet stay-behind forces and partisans pounced on logistical troops as soon as German spearheads disappeared.
- Gill, Henry A. (1998). Soldier Under Three Flags: Exploits of Special Forces' Captain Larry A. Thorne. Pathfinder Publishing, Inc. p. 45. ISBN 9780934793650. Retrieved 2013-09-28.
The Finns soon became seriously hindered and harassed by Soviet forces operating in their rear areas. Some of these units were left to operate as stay-behind or partisan units as the Soviets retreated.
- Packard, Martin (2008). Getting It Wrong: Fragments From a Cyprus Diary 1964. UK: AuthorHouse. p. 364. ISBN 978-1-4343-7065-5.
- Ballinger, Adam. The quiet Soldier. ISBN 978-1-85797-158-3.
- SMT-Verfahren im Zusammenhang mit der Kampfgruppe gegen Unmenschlichkeit (KgU), in: Bohse, Daniel/Miehe, Lutz (Hrsg.): Sowjetische Militärjustiz in der SBZ und frühen DDR: Tagungsband, Halle 2007.
- Koestler, Orwell und „Die Wahrheit": die Kampfgruppe gegen Unmenschlichkeit (KgU) und das heimliche Lesen in der SBZ/DDR 1948 bis 1959
- Ganser, Daniele, Nato's Secret Armies: Operation Gladio and Terrorism in Western Europe, ISBN 0-7146-5607-0.