Drawing extensively on recently released documents and private papers, this is the first book-length study to examine the intimate relationship between the Attlee government and Britain's intelligence and security services. Often praised for the formation of the modern-day welfare state, Attlee's government also played a significant role in combatting communism at home and overseas, often in the face of vocal, sustained, opposition from their own backbenches. Beneath Attlee's calm exterior lay a dedicated, if at times cautious, Cold War warrior. This study tells the story of Attlee's Cold War. At home, the Labour government implemented vetting to protect Whitehall and other areas of the state from communists, while, overseas, Attlee and his Foreign Secretary, Ernest Bevin authorised a series of highly-secret special operations in Eastern Europe. These operations, designed to erode Soviet influence, are presented here for the first time in significant detail. More widely, Ministers also strengthened Imperial and Commonwealth security and, responding to a series of embarrassing spy scandals, tried to revive Britain's vital nuclear transatlantic 'special relationship' with Washington. This study is essential reading for anyone interested in the Labour Party, intelligence, security and Britain's foreign and defence policy at the start of the Cold War.