Stay-behind also refers to a military tactic whereby specially trained soldiers let themselves be overrun by enemy forces in order to conduct intelligence, surveillance, target acquisition, and reconnaissance tasks often from pre-prepared hides.
According to Martin Packard they were "financed, armed, and trained in covert resistance activities, including assassination, political provocation and disinformation".
As late as 1996, the United Kingdom revealed to the German government the existence of stay-behind weapons and equipment caches in West Berlin.
In two of the secret caches, buried in the Grunewald forest, police found boxes with 9 mm pistols and ammunition, knives, navigation equipment, an RS-6 "spy radio", various manuals, tank- and aircraft-recognition books, a flask of brandy, and chocolate, as well as a copy of Total Resistance, the guerrilla warfare manual written in 1957 by Swiss Major Hans von Dach.
[5] The United Kingdom's Territorial Army regiments of SAS and Honourable Artillery Company provided such stay-behind parties in the UK's sector of West Germany.