The major doctrine that emerged to contend with the geopolitical tensions of the Cold War was the policy of containment. Formulated by U.S. diplomat George Kennan, this strategy aimed to prevent the spread of communism beyond its existing borders, particularly in Eastern Europe. Containment influenced U.S. foreign policy for decades, leading to various actions, including military interventions, alliances, and economic support for non-communist countries. The doctrine was evident in conflicts such as the Korean War and the Vietnam War, shaping international politics and contributing to the ideological confrontations that defined much of the 20th century.