This is the fourth volume of a comprehensive history of the British Communist Party in the 20th century. It begins with Russia's entry into World War II, which opended for a renewal of popular front politics. It examines the Labour governments of 1945 to 1951 and their relationships with the Communist Party, and documents the popular front from 1941 to 46. It analyzes the breakdown at a time of disappointment, with the entrenchment of the Cold War, and the electoral defeat of the Labour Party. The other three volumes in the series are: (volume 1) "The History of the Communist Party of Great Britain 1919-1924"; (volume 2) "The History of the Communist Party of Great Britain 1925-1926); (volume 3) "The History of the Communist Party of Great Britain 1927-1941". The first two books are written by James Klugman. Noreen Branson is the author of volumes 3 and 4.