The extreme isolationism that gripped the United States in the 1930s reinforced British appeasement and French paralysis. To Americans absorbed with their own distress, Hitler and Mussolini appeared as slightly ridiculous rabble-rousers on movie-house newsreels and certainly no concern of theirs. Moreover, the revisionist theory that the United States had been sucked into war in 1917 through the machinations of arms merchants or Wall Street bankers gained credence from the Senate’s Nye Committee inquiries of 1934–36. U.S. isolationism, however, had many roots: liberal abhorrence of arms and war, the evident failure of Wilsonianism, the Great Depression, and the revisionism of American historians, who were among the leaders in arguing that Germany was not solely responsible for 1914. Nor were isolationists restricted only to the Great Plains states or to one political party. Some members of Congress favoured punctilious defense of U.S. interests in the world but rejected involvement in the quarrels of others. Some were full-fledged pacifists even if it meant surrendering certain U.S. rights abroad. Left-wing isolationists warned that another great war would push the United States in the direction of Fascism. Conservative isolationists warned that another great war would usher in socialism.

These factions disputed among themselves over the wording of legislation, but their collective strength was enough to carry a number of bills designed to prevent a recurrence of the events of 1914–17. The Johnson Act of 1934 forbade American citizens to lend money to foreign countries that had not paid their past war debts. The Neutrality acts of 1935 and 1936 prohibited sale of war matériel to belligerents and forbade any exports to belligerents not paid for with cash and carried in their own ships. Thus, the United States was not to acquire a stake in the victory of any side or expose its merchant ships to submarines. (See the video.) The effect of these acts, however, was to preclude American aid to Abyssinia, Spain, and China, and thus hurt the victims of aggression more than the aggressors.

The United States did take steps in the 1930s, however, to mobilize the Western Hemisphere for the purposes of fighting the Depression and resisting European, especially German, encroachments. Roosevelt gave this initiative a name in his first inaugural address: the Good Neighbor Policy. Building on steps taken by Hoover, Roosevelt pledged nonintervention in Latin domestic affairs at the Montevideo Pan-American Conference of 1933, signed a treaty with the new Cuban government (May 29, 1934) abrogating the Platt Amendment, mediated a truce in the Chaco War between Bolivia and Paraguay in 1934 (with a peace treaty following in July 1938), and negotiated commercial treaties with Latin-American states. As war approached overseas, Washington also promoted pan-American unity on the basis of nonintervention, condemnation of aggression, no forcible collection of debts, equality of states, respect for treaties, and continental solidarity. The Declaration of Lima (1938) provided for pan-American consultation in case of a threat to the “peace, security, or territorial integrity” of any state.

Japan’s aggression in China

The first major challenge to American isolationism, however, occurred in Asia. After pacifying Manchukuo, the Japanese turned their sights toward North China and Inner Mongolia. Over the intervening years, however, the KMT had made progress in unifying China. The Communists were still in the field, having survived their Long March (1934–35) to Yen-an in the north, but Chiang’s government, with German and American help, had introduced modern roads and communications, stable paper currency, banking, and educational systems. How might Tokyo best round out its continental interests: by preemptive war or by cooperating with this resurgent China to expel Western influence from East Asia? The chief of the operations section of the Japanese general staff favoured collaboration and feared that an invasion of China proper would bring war with the Soviets or the Americans, whose economic potential he understood. Supreme headquarters, however, preferred to take military advantage of apparent friction between Chiang and a North China warlord. In September 1936, when Japan issued seven secret demands that would have made North China a virtual Japanese protectorate, Chiang rejected them. In December Chiang was even kidnapped by the commander of Nationalist forces from Manchuria, who tried to force him to suspend fighting the Communists and to declare war on Japan. This Sian Incident demonstrated the unlikelihood of Chinese collaboration with the Japanese program and strengthened the war party in Tokyo. As in 1931, hostilities began almost spontaneously and soon took on a life of their own.

An incident at the Marco Polo Bridge near Peking (then known as Pei-p’ing) on July 7, 1937, escalated into an undeclared Sino-Japanese war. Contrary to the Japanese analysis, both Chiang and Mao Zedong vowed to come to the aid of North China, while Japanese moderates failed to negotiate a truce or localize the conflict and lost all influence. By the end of July the Japanese had occupied Peking and Tientsin. The following month they blockaded the South China coast and captured Shanghai after brutal fighting and the slaughter of countless civilians. Similar atrocities accompanied the fall of Nanking on December 13. The Japanese expected the Chinese to sue for peace, but Chiang moved his government to Han-k’ou and continued to resist the “dwarf bandits” with hit-and-run tactics that sucked the invaders in more deeply. The Japanese could occupy cities and fan out along roads and rails almost at will, but the countryside remained hostile.

World opinion condemned Japan in the harshest terms. The U.S.S.R. concluded a nonaggression pact with China (August 21, 1937), and Soviet-Mongolian forces skirmished with Japanese on the border. Britain vilified Japan in the League, while Roosevelt invoked the Stimson Doctrine in his “quarantine speech” of October 5. But Roosevelt was prevented by the Neutrality acts from aiding China even after the sinking of U.S. and British gunboats on the Yangtze.

On March 28, 1938, the Japanese established a Manchukuo-type puppet regime at Nanking, and spring and summer offensives brought them to the Wu-han cities (chiefly Han-k’ou) on the Yangtze. Chiang stubbornly moved his government again, this time to Chungking, which the Japanese bombed mercilessly in May 1939, as they did Canton for weeks before its occupation in October. Such incidents, combined with the Nazi and Fascist air attacks in Spain and Abyssinia, were omens of the total war to come. The United States finally took a first step in opposition to Japanese aggression on July 29, 1939, announcing that it would terminate its 1911 commercial treaty with Japan in six months and thereby cut off vital raw materials to the Japanese war machine. It was all Roosevelt could do under existing law, but it set in train the events that would lead to Pearl Harbor.