The wartime alliance with the Soviet Union broke down before the end of 1945, reviving the fear of communism that had appeared in the Red Scare of the 1920s. Domestically, fear focused on the threat of Communist subversion of the government, a fear exploited by Sen. Joseph R. McCarthy, who created panic by sensational but unfounded charges against the nation's leaders (including President Harry S. Truman, Secretary of State Dean Acheson, and Gen. George C. Marshall), accusing them of shielding traitors. Abroad, the focus was on the spread of Soviet control over Eastern Europe and Asia. The possibility of nuclear war between the United States and the Soviet Union led the Civil Defense Agency to post signs in public buildings pointing to fallout shelters and to encourage homeowners to build backyard shelters. In subsequent decades, tension with the Soviet Union and Communist China continued to disrupt American life, notably when the United States led a United Nations effort to halt communist expansion in Korea (1950-53), a "police action" that required deployment of almost 1.8 million troops, cost more than 33,000 American lives, and drew little support from the American people; and even more so in the Vietnam War (1964-75), when the United States tried in vain to prevent the Communist regime in North Vietnam from defeating South Vietnam. Other episodes, such as the 1957 Soviet launching of the Sputnik satellite and the 1962 Cuban Missile Crisis, added to the tension.