Roosevelt's and Churchill's was a unique relationship, based on interlinked national histories, partially shared nationality - Churchill was half-American - similarities in class and education, love for the navy, and a common belief in the superiority of Anglo-Saxon institutions. It was cemented by shared enemies: Nazi Germany and Imperial Japan. On these foundations, Churchill and Roosevelt constructed a fighting alliance unlike any other in history, with a Combined Chiefs of Staff, Anglo-American war-making boards, and an atomic alliance that delivered victory in 1945. The two men also developed an extraordinary personal relationship, communicating almost daily by telegram, telephone, personal meetings and through intermediaries. Their camaraderie ended abruptly with FDR's death on 12 April 1945, just hours before American and British troops liberated Buchenwald and Belsen. At the heart of this special relationship, hidden by layers of secrecy, was an extraordinary and far-reaching sharing of intelligence. Regarding this as the "touchstone" of their mutual trust, this biography explores their relationship.