The Cold War lasted from 1945 to 1991 and involved political and military tensions between the United States and the Soviet Union. Key events included the Yalta and Potsdam conferences dividing post-WWII Europe, the Truman Doctrine providing aid to countries resisting communism, and the erection of the Berlin Wall in 1961 separating East and West Berlin. Other notable developments were the Space and Arms Races, wars in Korea and Vietnam, and Mao Zedong's rule in China including the Great Leap Forward and Cultural Revolution.