The first such network was established in Belgium as early as 1944, but it was only after the end of World War II that the stay-behind system became a clandestine West European-wide network. The network was conceived as a collective security system by the U.S. government working in cooperation with friendly intelligence agencies. The stay-behind network was placed into operation in 1948 by the National Security Council (NSC) and was funded by the Central Intelligence Agency (CIA) and supervised by CIA personnel, working in close cooperation with their European counterparts.
West European governments were moving in a similar direction. The 1948 Brussels Treaty created a Clandestine Committee of the Western Union (CCWU), based in Paris. In 1951 it was transformed into the Clandestine Planning Committee (CPC). The CPC was linked to NATO in coordination with the Supreme Headquarters Allied Powers Europe (SHAPE). It was under this umbrella that the NATO states organized and coordinated the stay-behind network.
In the beginning, organization and supervision of the networks was divided between the United States and the United Kingdom. The British were responsible for operations in Belgium, France, Holland, Norway, and Portugal, whereas the Americans took responsibility for Sweden, Finland, and the remaining countries of Western Europe not covered by the British. Nevertheless, it was not until 1957 that the secret network became a fully integrated system. The CPC established two subcommittees, one of which was the Allied Coordination Committee (ACC), that became responsible for coordinating the stay-behind structures in Belgium, Denmark, France, Germany, Italy, Luxembourg, Holland, Norway, the United Kingdom, and the United States. The ACC's main duties were to produce policies for the network and to further develop its clandestine capabilities as well as bases located in the United Kingdom and the United States.
Those recruited for the network, no matter what their national origin, were supposed to organize clandestine bases and plan operations. The network had both wartime and peacetime duties. In peacetime organizers were to recruit and train personnel, whereas in wartime they planned stay-behind operations in conjunction with SHAPE.
The most famous example of the stay-behind network was in Italy. Officially set up during 1956–1958, it was known as Gladio. There operating bases and trained units were created as a result of a partnership between the Central Intelligence Agency and the Italian secret services with the aim of preventing Soviet aggression and also internal communist subversion. It was only in 1990 that the Italian government dismantled Gladio and that a parliamentary commission declared it clandestine and illegal.
In the 1980s the ACC organized yearly international exercises. According to published sources, the last ACC meeting was held in October 1990. Since then the network has been disbanded in most West European countries. In the early 1990s, many governments formally admitted existence of the network and dismantled it.
Ganser, Daniele. NATO's Top Secret Stay-Behind Armies and Terrorism in Western Europe. New York: Frank Cass, 2005.; Willems, Jan, ed. Gladio. Paris: Reflex, 1991.