After World War II, Sweden faced the looming threat of the Soviet Union and its efforts to spread communism. This led to the formation of a resistance movement involving the Swedish Security Service, the employers' association, and the labor movement. The stay-behind network was fully legalized in 1955 and continued its clandestine operations until the mid-1990s, aiming to keep communismand the Sovietsout of Sweden. Based on extensive archival research and interviews with key figures, author Johan Wennström unveils the secrets surrounding the stay-behinds. The book sheds light on the men who founded the network, the work of its agents, the cell-like structure they relied upon, and the collaboration between the US and British intelligence services and the Swedish stay-behinds. It is the first comprehensive study of a secret organization that helped shape modern Sweden. Furthermore, it provides lessons for today's NATO and advocates for a defense policy that is oriented towards national interests.