Although relations between the Soviet Union and the United States had been strained in the years before World War II, the U.S.-Soviet alliance of 1941–1945 was marked by a great degree of cooperation and was essential to securing the defeat of Nazi Germany. The Cold War was an ongoing political rivalry between the United States and the Soviet Union and their respective allies that developed after World War II. This hostility between the two superpowers was first given its name by George Orwell in an article published in 1945.