Although it produced no antiwar movement, the Korean War (1950–1953) was an unpopular and difficult conflict for the American people. This limited war, which lasted

U.S. Marines resting in the snow somewhere en route after fighting their way from the communist encirclement at Chosin to Hungnam, Korea, in December 1950. AP/WIDE WORLD PHOTOS

three years and took the lives of more than 33,000 U.S. troops in combat, ended with only small adjustments in the boundary between North and South Korea. But it had large effects on U.S. politics and brought major changes to U.S. national security policy during the Cold War (1946–1991).

Cold War considerations compelled President Harry Truman's decision to commit U.S. combat forces to the defense of South Korea in June 1950. Truman believed that the North Korean invasion was a direct challenge from the Kremlin and that U.S. credibility...