On Saturday, 24 June 1950, U.S. Secretary of State Dean Acheson informed President Truman that the North Koreans had invaded South Korea. Truman and Acheson discussed a U.S. invasion response and agreed that the United States was obligated to act, paralleling the North Korean invasion with Adolf Hitler's aggressions in the 1930s, with the conclusion being that the mistake of appeasement must not be repeated. Several U.S. industries were mobilized to supply materials, labor, capital, production facilities, and other services necessary to support the military objectives of the Korean War. However, President Truman later acknowledged that he believed fighting the invasion was essential to the American goal of the global containment of communism as outlined in the National Security Council Report 68 (NSC-68) (declassified in 1975):
Try to answer this question if possible (otherwise reply "unanswerable"): What did the US not want to see repeated?
the mistake of appeasement