The Breakdown of the Grand Alliance and the Origins of the Cold War, 1942-1946 starts with the evidence that the Soviet Union and its two Allies were initially aiming to achieve post-war cooperation over the nature of the international system and maintaining that cooperation after peace was established it then provides a detailed explanation of how that commitment began to be questioned from September 1944 and an analysis of why aggressive policies began to supersede those of cooperation from 31 December 1944 partly. Particular attention is paid to Poland, Romania, Germany, and the countries bordering on the northern and southern Mediterranean shores in which the UK and USSR had particular interests. The conferences of Yalta and Potsdam are covered while also examining Tehran, and the initial Councils of Foreign Ministers are given considerable attention, along with the possibilities raised of extending the two temporary 1944 spheres of influence arrangements.