The Belgian stay-behind network, colloquially called "Gladio" (meaning "sword"), was a secret mixed civilian and military unit, trained to form a resistance movement in the event of a Soviet invasion and part of a network of similar organizations in North Atlantic Treaty Organization states. It functioned from at least 1951 until 1990, when the Belgian branch was promptly and officially dissolved after its existence became publicly known following revelations concerning the Italian branch of the stay-behind network.