<P> The 20th century was marked by two world wars in which Allied powers, along with the United States, defeated their enemies and through this participation the United States increased its international reputation . President Wilson's Fourteen Points was developed from his idealistic Wilsonianism program of spreading democracy and fighting militarism so as to end any wars . It became the basis of the German Armistice (which amounted to a military surrender) and the 1919 Paris Peace Conference . The resulting Treaty of Versailles, due to European allies' punitive and territorial designs, showed insufficient conformity with these points and the U.S. signed separate treaties with each of its adversaries; due to Senate objections also, the U.S. never joined the League of Nations, which was established as a result of Wilson's initiative . In the 1920s, the United States followed an independent course, and succeeded in a program of naval disarmament, and refunding the German economy . Operating outside the League it became a dominant player in diplomatic affairs . New York became the financial capital of the world, but the Wall Street Crash of 1929 hurled the Western industrialized world into the Great Depression . American trade policy relied on high tariffs under the Republicans, and reciprocal trade agreements under the Democrats, but in any case exports were at very low levels in the 1930s . </P> <P> The United States adopted a non-interventionist foreign policy from 1932 to 1938, but then President Franklin D. Roosevelt moved toward strong support of the Allies in their wars against Germany and Japan . As a result of intense internal debate, the national policy was one of becoming the Arsenal of Democracy, that is financing and equipping the Allied armies without sending American combat soldiers . Roosevelt mentioned four fundamental freedoms, which ought to be enjoyed by people "everywhere in the world"; these included the freedom of speech and religion, as well as freedom from want and fear . Roosevelt helped establish terms for a post-war world among potential allies at the Atlantic Conference; specific points were included to correct earlier failures, which became a step toward the United Nations . American policy was to threaten Japan, to force it out of China, and to prevent its attacking the Soviet Union . However, Japan reacted by an attack on Pearl Harbor in December 1941, and the United States was at war with Japan, Germany, and Italy . Instead of the loans given to allies in World War I, the United States provided Lend - Lease grants of $50,000,000,000 . Working closely with Winston Churchill of Britain, and Joseph Stalin of the Soviet Union, Roosevelt sent his forces into the Pacific against Japan, then into North Africa against Italy and Germany, and finally into Europe starting with France and Italy in 1944 against the Germans . The American economy roared forward, doubling industrial production, and building vast quantities of airplanes, ships, tanks, munitions, and, finally, the atomic bomb . Much of the American war effort went to strategic bombers, which flattened the cities of Japan and Germany . </P> <P> After the war, the U.S. rose to become the dominant non-colonial economic power with broad influence in much of the world, with the key policies of the Marshall Plan and the Truman Doctrine . Almost immediately, however, the world witnessed division into broad two camps during the Cold War; one side was led by the U.S. and the other by the Soviet Union, but this situation also led to the establishment of the Non-Aligned Movement . This period lasted until almost the end of the 20th century and is thought to be both an ideological and power struggle between the two superpowers . A policy of containment was adopted to limit Soviet expansion, and a series of proxy wars were fought with mixed results . In 1991, the Soviet Union dissolved into separate nations, and the Cold War formally ended as the United States gave separate diplomatic recognition to the Russian Federation and other former Soviet states . </P> <P> In domestic politics, foreign policy is not usually a central issue . In 1945--1970 the Democratic Party took a strong anti-Communist line and supported wars in Korea and Vietnam . Then the party split with a strong, "dovish", pacifist element (typified by 1972 presidential candidate George McGovern). Many "hawks", advocates for war, joined the Neoconservative movement and started supporting the Republicans--especially Reagan--based on foreign policy . Meanwhile, down to 1952 the Republican Party was split between an isolationist wing, based in the Midwest and led by Senator Robert A. Taft, and an internationalist wing based in the East and led by Dwight D. Eisenhower . Eisenhower defeated Taft for the 1952 nomination largely on foreign policy grounds . Since then the Republicans have been characterized by a hawkish and intense American nationalism, and strong opposition to Communism, and strong support for Israel . </P>

What idea was used to justify u.s. foreign policy during the cold war era