This article gives an overview of what we now know from trustworthy sources about the origins, character, and development of the “stay-behind” networks established in Western Europe during the early Cold War in preparation for a possible Soviet invasion and occupation. The article critically examines and refutes several notions about Stay Behind that have tended to dominate writings on the subject, such as allegations that the networks in Italy and other West European countries were mere creations of the U.S. Central Intelligence Agency and the British Secret Intelligence Service; that they were controlled by the North Atlantic Treaty Organization as its “secret army”; and that in at least some countries they pursued terrorist activities directed against left-wing groups suspected of working to overthrow the established order.