Packed with first-hand accounts and previously classified government documents, this book reveals the secrets of Sweden's resistance network, created to deter a potential Soviet occupation. Following World War II, Sweden faced the looming threat of the Soviet Union and its drive to spread communism. This led to the formation of a resistance movement involving Sweden's intelligence service, the employers' association and the labour movement. The stay-behind network was fully legalised in 1955 and continued its clandestine work until the mid-1990s, with the mission of keeping communism – and the Soviets – out of Sweden. Drawing on extensive archival research and interviews with key figures, author Johan Wennström peels back the layers of secrecy surrounding the stay-behinds. This book looks at the men who created the network, the work the operatives carried out, the cell-like structure they relied on, and how the US and UK intelligence communities cooperated with the Swedish stay-behinds. This is the first in-depth study of a secret organization that helped shape modern Sweden. It also highlights lessons for today's NATO and makes the case for a defence policy grounded in national interest.