The spirit of isolationism eroded steadily as Americans watched the aggressive moves of Adolf Hitler and his allies. President Roosevelt and the American people finally concluded that the United States could not survive as a nation, nor could Western civilization endure, if Hitler and fascism gained dominance over Europe. During the world war that followed, the American nation rose to the status of a major world power, a position that was not abandoned but confirmed in the cold-war years of the late 1940s and the 1950s.

Total War: 1941-45. In September 1940, Congress established the first peacetime draft in American history, and 6 months later it authorized Roosevelt to transfer munitions to Great Britain, now standing practically alone against Hitler, by a procedure called Lend-Lease. On Dec. 7, 1941, the Japanese reacted to stiffening American diplomacy against its expansion into Southeast Asia by attacking the U.S. fleet at Pearl Harbor in the Hawaiian Islands. This thrust was aimed at immobilizing American power long enough to allow the establishment of a wide imperial Japanese perimeter including all of the western Pacific and China, henceforth to be defended against all comers. Japan, however, in one stroke had succeeded in scuttling American isolationist sentiment, forcing the United States into World War II, and unifying the American people as never before in total war.

The first American military decision was to concentrate on defeating Hitler while fighting a holding action in the Pacific. The next was to form an alliance with Great Britain so close that even military commands were jointly staffed. The year 1942 was devoted to halting, after many defeats, the outward spread of Japanese power and to keeping Hitler's forces from overwhelming America's British and Soviet allies. Large shipments of munitions went to both allies. In November an American force invaded North Africa; it joined the British in defeating the German armies in that region by May 1943.

In 2 months the Allies were fighting the Germans in Sicily and Italy; at the same time U.S. forces in the Pacific were pushing in toward the Japanese home islands by means of an island-hopping offensive. On the long Russian front, German armies were being defeated and pushed back toward their borders. In June 1944 a huge Allied force landed on the French coast, an invasion preceded by 2 years of intense day-and-night bombing of Germany by British and American aircraft. By August 1944, Paris was recaptured. Hitler's empire was crumbling; clouds of bombers were raining destruction on German cities; and on Apr. 30, 1945, with the Soviet troops just a few miles from Berlin, Hitler committed suicide. Peace in Europe followed shortly.

The Pacific war continued, the Japanese home islands being rendered practically defenseless by July 1945. American aerial attacks burned out city after city. In April, Harry S. Truman had succeeded to the presidency on Roosevelt's death. Now, advised that the alternative would be an invasion in which multitudes would perish, including many thousands of young Americans, he authorized use of the recently tested atomic bomb. On Aug. 6, the city of Hiroshima was obliterated; on Aug. 9, the same fate came to Nagasaki. Within a week, a cease-fire (which later research suggests was reachable without atomic attack) was achieved.

The political shape of the postwar world was set at the Yalta Conference (February 1945) between Roosevelt, Joseph Stalin, and Winston Churchill. Soviet occupation of Eastern European countries overrun by the Red Army was accepted, in return for a pledge to allow democratic governments to rise within them. Soviet and Allied occupation zones in Germany were established, with Berlin, deep in the Soviet zone, to be jointly administered. In return for Soviet assistance in the invasion of Japan (which was eventually not needed), it was agreed that certain possessions in the Far East and rights in Manchuria, lost to the Japanese long before, would be restored to the USSR. Soon it was clear that the kind of democratic government envisioned by the Americans was not going to be allowed in the East European countries under Soviet control. Nor, as the Soviets pointed out, was the United States ready to admit the Soviets to any role in the occupation and government of Japan, whose internal constitution and economy were rearranged to fit American desires under Gen. Douglas MacArthur.

Cold-War Years. The breach widened steadily. Charges and countercharges were directed back and forth, the Soviets and Americans interpreting each other's actions in the worst possible light. Americans became convinced that the Soviets were thrusting out in every direction, seeking to communize not only the Soviet-occupied countries, but also Turkey, Greece, and Western Europe. In February 1946, Stalin declared in Moscow that there could never be a lasting peace with capitalism. Shortly thereafter, Churchill warned of the Iron Curtain that had descended across the middle of Europe. The cold war had begun.

In March 1947, Truman asked Congress for funds to shore up Turkey and Greece, both under Soviet pressure, and announced the Truman Doctrine: that "it must be the policy of the United States to support free peoples who are resisting attempted subjugation by armed minorities or by outside pressures." Then the Marshall Plan (named for George C. Marshall, U.S. chief of staff during the war and at this time secretary of state), approved by Congress in April 1948, sent $12 billion to the devastated countries of Europe to help them rebuild and fend off the despair on which communism was believed to feed.

True to its Democratic tradition, the Truman administration stressed multilateral diplomacy; that is, the building of an international order based on joint decision making. Nationalism, it was believed, must be tamed. The United Nations received strong American support. Meanwhile, the United States continued the drive toward a lowering of world tariffs (begun in the 1930s). During the war, all recipients of Lend-Lease had been required to commit themselves to lowered tariffs. These commitments were internationally formalized in 1947 in the General Agreement on Tariffs and Trade, when 23 nations participated in an extensive mutual lowering of trade barriers. In 1948, at American initiative, the Organization of American States was established to provide a regional multilateral consultative body in the Western Hemisphere. Within Europe, the Marshall Plan required the formation of Europe-wide organizations, leading eventually to the Common Market.

Toward the USSR, the basic American policy was that known as containment: building "situations of strength" around its vast perimeter to prevent the outward spread of communism. Angered Americans blamed the USSR for world disorder and came to regard the peace of the entire world as a U.S. responsibility. After their immense war effort, many Americans believed that the United States could accomplish whatever it desired to do. Also, having defeated one form of tyranny, fascism, and now being engaged in resisting another, Stalinist communism, the American people assumed with few questions that, since their cause was just, whatever they did in its name was right. Critics of national policy were harshly condemned.

A series of East-West crises, most dramatically the Berlin Blockade of 1948-49, led to the creation (April 1949) of the North Atlantic Treaty Organization. The NATO alliance sought to link the United States militarily to Western Europe (including Greece and Turkey) by making an attack against one member an attack against all. As Europe recovered its prosperity, the focus of East-West confrontation shifted to Asia, where the British, French, and Dutch empires were collapsing and the Communist revolution in China was moving toward its victory (October 1949). In June 1950 the North Korean army invaded South Korea. The United Nations Security Council (which the Soviets were then boycotting) called on UN members jointly to repel this attack. Shortly afterward, a multinational force under Gen. Douglas MacArthur was battling to turn back North Korean forces in the Korean War. As the UN army swept northward to the Manchurian border, Chinese forces flooded southward to resist them, and a long, bloody seesaw war ensued. An armistice was not signed until July 1953, following 150,000 American casualties and millions of deaths among the Koreans and Chinese.

Domestic Developments during the Truman Years. In 1945, President Truman called on Congress to launch another program of domestic reform, but the nation was indifferent. It was riding a wave of affluence such as it had never dreamed of in the past. Tens of millions of people found themselves moving upward into a middle-class way of life. The cold war, and the pervasive fear of an atomic war, induced a trend toward national unity and a downplaying of social criticism. The Atomic Energy Act of 1946 nationalized nuclear power, putting it under civilian control, but no other bold departures were made. What fascinated Americans was the so-called baby boom-a huge increase in the birthrate (the population was at 150 million by 1950 and 179 million by 1960)-and the need to house new families and teach their children.

In the presence of rapidly rising inflation, labor unions called thousands of strikes, leading in 1948 to passage of the Taft-Hartley Act, which limited the powers of unions, declared certain of their tactics "unfair labor practices," and gave the president power to secure 80-day "cooling off periods" by court injunction. As union benefits increased nationwide, however, industrial warfare quieted. In 1948 the United Automobile Workers won automatic "cost of living" pay increases in their contracts and in 1955 the guaranteed annual wage. In 1955 merger negotiations were completed for the formation of the American Federation of Labor and Congress of Industrial Organizations ( AFL-CIO); more than 85% of all union members were now in one organization.

Fears that Russian communism was taking over the entire world were pervasive during the Truman years. Soviet spy rings were discovered in the United States, Canada, and Great Britain. In 1948-50 a sensational trial for perjury led to the conviction of a former State Department official, Alger Hiss, on the grounds that while in the department he had been part of a Communist cell and had passed secrets to the Soviets. In 1950 a Soviet spy ring was uncovered in the Los Alamos atomic installation. These events, together with the explosion (1949) of a Soviet atomic bomb and the victory (1949) of the Communists in China, prompted a widespread conviction that subversive conspiracies within the American government were leading toward Soviet triumph.

In February 1950, Republican Sen. Joseph R. McCarthy of Wisconsin began a 4-year national crisis, during which he insisted repeatedly that he had direct evidence of such conspiracies in the federal government, even in the army. The entire country seemed swept up in a hysteria in which anyone left of center was attacked as a subversive. A program to root out alleged security risks in the national government led to a massive collapse in morale in its departments; it destroyed the State Department's corps of experts on Far Eastern and Soviet affairs. The Truman administration's practice of foreign policy was brought practically to a halt. In 1952, Dwight D. Eisenhower, nationally revered supreme commander in Europe during World War II, was elected president (1953-61) on the Republican ticket, but soon McCarthy was attacking him as well for running a "weak, immoral, and cowardly" foreign policy. In 1954 the long and dramatic Army-McCarthy hearings, the first congressional hearings to be nationally televised, destroyed McCarthy's credibility. He was censured by the Senate, and a measure of national stability returned.

The Eisenhower Years. Eisenhower declared himself uninterested in repealing the New Deal, but he was socially and economically conservative and his presidency saw the enactment of few reforms. His appointment of Earl Warren as chief justice of the Supreme Court, however, led to a Court that suddenly seized so bold and active a role in national life that many called it revolutionary. During Warren's long tenure (1953-69), the Court swept away the legal basis for racial discrimination; ruled that every person must be represented equally in state legislatures and in the U.S. House of Representatives; changed criminal-justice procedures by ensuring crucial rights to the accused; broadened the artist's right to publish works shocking to the general public; and in major ways limited the government's ability to penalize individuals for their beliefs or associations.

No decision of the Warren Court was more historic than that in Brown v. Board of Education of Topeka, Kansas (1954), which ruled unanimously that racial segregation in the public schools was unconstitutional. This great decision-followed by others that struck down segregation in all public facilities and in elections and marriage laws-sparked a revolution in race-relations law. The separate-but-equal principle was cast aside, and the Second Reconstruction could get underway. Now black Americans could charge that the statutory discrimination that tied them down and kept them in a secondary caste was illegal, a fact that added enormous moral weight to their cause. Resistance by southern whites to desegregated public education would make the advance of that cause frustratingly slow, however. By 1965 black children had been admitted to white schools in fewer than 25% of southern school districts. The fight for racial equality was not limited to the South, for by 1960 only 60% of black Americans remained there; 73% of them also lived in cities: they were no longer simply a scattered, powerless rural labor force in the South.

In 1957 the Soviet government launched its first orbiting satellite, Sputnik, and a national controversy erupted. Why are we so far behind in the crucial area of rocketry? Americans asked. Many critics replied that weaknesses in public education, especially in science and technology, were the root cause. In 1958, Congress enacted the first general education law since the Morrill Act of 1862-the National Defense Education Act. It authorized $1 billion for education from primary level through university graduate training, inaugurating a national policy that became permanent thereafter and that resulted in the spending of huge sums and the transformation of American public education.

Eisenhower's foreign policy, under Secretary of State John Foster Dulles, was more nationalist and unilateral than Truman's. American-dominated alliances ringed the Soviet and Chinese perimeters. Little consultation with Western European allies preceded major American initiatives, and in consequence the United States and Western Europe began drifting apart. Persistent recessions in the American economy hobbled the national growth rate while the Soviet and Western European economies surged dramatically. An aggressive Nikita Khrushchev, Soviet premier, trumpeted that communism would bury capitalism and boasted of Moscow's powerful intercontinental missiles while encouraging so-called wars of liberation in Southeast Asia and elsewhere.