This document provides an overview of the origins of the Cold War between the United States and Soviet Union following World War II. It discusses the wartime alliance between the US, Britain, and Soviet Union which was pragmatic but lacked trust. At conferences like Tehran, Yalta, and Potsdam, the Allied leaders were unable to resolve disagreements over the post-war structure of Europe. As the Soviets exerted control over Eastern Europe, tensions rose further and the Cold War began, marked by the Iron Curtain speech in 1946 and the formation of opposing military alliances like NATO.