In April 1945 Churchill said to Sir Alan Brooke, Chief of the Imperial General Staff, 'There is only one thing worse than fighting with allies, and that is fighting without them!' When he became Prime Minister on 10 May 1940 Churchill was without allies. Dunkirk and the Battle of Britain saved Britain from immediate defeat, but it was evident that Britain alone could never win the war. Churchill looked to America. He said that until Pearl Harbor 'no lover ever studied every whim of his mistress as I did those of President Roosevelt'. But would Roosevelt have entered the war if Pearl Harbor had not taken place? Until then his actions were ambivalent, and even afterwards America's policy was largely shaped by self-interest and her idea of what a postwar world should be like. Churchill's account of relations with his allies and associates was sanitized for the historical record and has been accepted uncritically. In reality he had to battle with the generals and the CIGS, Tory backbenchers and the War Cabinet, de Gaulle and the Free French and - above all - the Americans. Even his wife, Clementine, could on occasions be remarkably unsupportive. Walter Reid, the author of several acclaimed works on 20th-century military history, brings together the result of recent research to create a powerful narrative which reveals how much time and energy was devoted to fighting the war that was excluded from the official accounts, the war with the allies.