Gladio refers to a covert NATO operation that began during the Cold War, primarily in Europe. Its main purpose was to prepare for potential Soviet invasions by establishing secret paramilitary groups. These groups were trained to conduct guerrilla warfare and sabotage, ensuring that resistance could be mounted against any occupying forces. The operation was revealed in the early 1990s, leading to significant controversy and debate. Critics argue that some of these groups engaged in illegal activities, including terrorism, to manipulate political outcomes. The legacy of Gladio continues to influence discussions about state-sponsored covert operations and their ethical implications.