Klaus Fuchs was one of the most infamous spies of the Cold War, whose espionage feats altered the nature of the early postwar period. Drawing on newly released archival documents and witness testimony, this article considers the events surrounding his arrest and conviction. These sources reveal that even before Fuchs was arrested, he was used as a pawn.Because of his supreme importance to the British nuclear weapons program, some British of ficials initially believed that he should remain in his position, despite his admission of guilt. Until the matter was resolved, Fuchs was used unwittingly as a wedge between the British and U.S. intelligence services.Moreover, when the United States criticized British security standards, the Fuchs case was used by MI5 to cajole and mislead Parliament and the public.