The United States joined the war in 1941, two years after Europe exploded into conflict in 1939. However, the path to the Japanese bombing of Pearl Harbor, the surprise attack that threw the United States headlong into war, began much earlier than that. For the Empire of Japan, the war had begun a decade before Pearl Harbor.

South Manchuria Railway Incident

Figure 1. Imperial Japanese Army Infantry in Manchuria.

A False Flag Attack on Japan

On September 18, 1931, a small explosion tore up railroad tracks controlled by the Japanese-owned South Manchuria Railway near the city of Shenyang (Mukden) in the Chinese province of Manchuria. The railway company condemned the bombing as the work of anti-Japanese Chinese dissidents. Evidence, though, suggests that the initial explosion was neither an act of Chinese anti-Japanese sentiment nor an accident but an elaborate ruse planned by the Japanese to provide a basis for invasion. In response, the privately operated Japanese Guandong (Kwangtung) army began shelling the Shenyang garrison the next day, and the garrison fell before nightfall.

Japan Invades Manchuria

Hungry for Chinese territory and witnessing the weakness and disorganization of Chinese forces, but under the pretense of protecting Japanese citizens and investments, the Japanese Imperial Army ordered a full-scale invasion of Manchuria. The invasion was swift. Without a centralized Chinese army, the Japanese quickly defeated isolated Chinese warlords and by the end of February 1932, all of Manchuria was firmly under Japanese control. Japan established the nation of Manchukuo out of the former province of Manchuria.

Figure 2. Japanese troops entering Tsitsihar

This seemingly small skirmish—known by the Chinese as the September 18 Incident and the Japanese as the Manchurian Incident—sparked a war that would last thirteen years and claim the lives of over thirty-five million people. Comprehending Japanese motivations for attacking China and the grueling stalemate of the ensuing war are crucial for understanding Japan’s seemingly unprovoked attack on Pearl Harbor, Hawaii, on December 7, 1941, and, therefore, for understanding the involvement of the United States in World War II as well.

Economic Hardships Challenge Japan’s Leaders

Despite their rapid advance into Manchuria, the Japanese put off the invasion of China for nearly three years. Japan occupied a precarious domestic and international position after the September 18 Incident. At home, Japan was split by political factionalism due to its stagnating economy. Leaders were torn as to whether to address modernization and lack of natural resources through unilateral expansion (the conquest of resource-rich areas such as Manchuria to export raw materials to domestic Japanese industrial bases such as Hiroshima and Nagasaki) or international cooperation (a philosophy of pan-Asianism in an anti-Western coalition that would push the colonial powers out of Asia).

Ultimately, after a series of political crises and assassinations enflamed tensions, pro-war elements within the Japanese military triumphed over the more moderate civilian government. Japan committed itself to aggressive military expansion.

League of Nations Finds Japan at Fault

Chinese leaders Chiang Kai-shek and Zhang Xueliang appealed to the League of Nations for assistance against Japan. The United States supported the Chinese protest, proclaiming the Stimson Doctrine in January 1932, which refused to recognize any state established as a result of Japanese aggression. Meanwhile, the League of Nations sent Englishman Victor Bulwer-Lytton to investigate the September 18 Incident. After a six-month investigation, Bulwer-Lytton found the Japanese guilty of inciting the September 18 incident and demanded the return of Manchuria to China. The Japanese withdrew from the League of Nations in March 1933.

Figure 3. In 2013, visitors view images of survivors of the Nanjing Massacre Memorial Hall in China.

Japan isolated itself from the world. Its diplomatic isolation empowered radical military leaders who could point to Japanese military success in Manchuria and compare it to the diplomatic failures of the civilian government. The military took over Japanese policy. And in the military’s eyes, the conquest of China would not only provide for Japan’s industrial needs, it would secure Japanese supremacy in East Asia.

Japan Invades China

Japanese Expansion

Japanese military planners, believing that American intervention was inevitable, planned a coordinated Pacific offensive to neutralize the United States and other European powers and provide time for Japan to complete its conquests and fortify its positions. Like its European allies, Japan was intent upon creating an empire for itself.

In 1931, it created a new nation, a puppet state called Manchukuo, which had been cobbled together from the three northernmost provinces of China. Although the League of Nations formally protested Japan’s seizure of Chinese territory in 1931 and 1932, it did nothing else. In 1937, a clash between Japanese and Chinese troops, known as the Marco Polo Bridge Incident, led to a full-scale invasion of China by the Japanese. By the end of the year, the Chinese had suffered a series of defeats. In Nanjing, then called Nanking by Westerners, Japanese soldiers systematically raped Chinese women and massacred hundreds of thousands of civilians, leading to international outcry.

Figure 4. This map shows the growing reach of the Japanese empire during WWII.

China’s Scorched Earth Policy Provides Propaganda for the Chinese Communist Party

To halt the invading enemy, Chiang Kai-shek adopted a scorched-earth strategy of “trading space for time.” His Nationalist government retreated inland, burning villages and destroying dams, and established a new capital at the Yangtze River port of Chongqing (Chungking). Although the Nationalists’ scorched-earth policy hurt the Japanese military effort, it alienated scores of dislocated Chinese civilians and became a potent propaganda tool of the emerging Chinese Communist Party (CCP).

American Response

Public sentiment against Japan in the United States reached new heights. Members of Protestant churches that were involved in missionary work in China were particularly outraged, as were Chinese Americans. A troop of Chinese American Boy Scouts in New York City’s Chinatown defied Boy Scout policy and marched in protest against Japanese aggression.

Americans read about the brutal fighting in China, but the United States lacked both the will and the military power to oppose the Japanese invasion. After the gut-wrenching carnage of World War I, many Americans retreated toward isolationism by opposing any involvement in the conflagrations burning in Europe and Asia. And even if Americans wished to intervene, their military was lacking. The Japanese army was a technologically advanced force consisting of 4,100,000 men and 900,000 Chinese collaborators—and that was in China alone. The Japanese military was armed with modern rifles, artillery, armor, and aircraft. By 1940, the Japanese navy was the third-largest and among the most technologically advanced in the world.

Soong May-ling Lobbies Washington

Still, Chinese Nationalists lobbied Washington for aid. Chiang Kai-shek’s wife, Soong May-ling—known to the American public as Madame Chiang—led the effort. Born into a wealthy Chinese merchant family in 1898, Madame Chiang spent much of her childhood in the United States and graduated from Wellesley College in 1917 with a major in English literature. In contrast to her gruff husband, Madame Chiang was charming and able to use her knowledge of American culture and values to garner support for her husband and his government. But while the United States denounced Japanese aggression, it took no action during the 1930s.

As Chinese Nationalists fought for survival, the Communist Party was busy collecting people and supplies in the northwestern Shaanxi Province. China had been at war with itself when the Japanese came. Nationalists battled a stubborn communist insurgency. In 1935 the Nationalists threw the communists out of the fertile Chinese coast, but an ambitious young commander named Mao Zedong recognized the power of the Chinese peasant population. In Shaanxi, Mao recruited from the local peasantry, building his force from a meager seven thousand survivors at the end of the Long March in 1935 to a robust 1.2 million members by the end of the war.

Although Japan had conquered much of the country, the Nationalists regrouped and the communists rearmed. An uneasy truce paused the country’s civil war and refocused efforts on the invaders. The Chinese could not dislodge the Japanese, but they could stall their advance. The war mired in stalemate.

Anti-Communist and Pro-Capitalist Sentiments in Japan

Militaristic politicians took control of Japan in the 1930s. The Japanese had worked assiduously for decades to modernize, build their strength, and become a prosperous, respected nation. The sentiment in Japan was decidedly pro-capitalist, and the Japanese militarists were fiercely supportive of a capitalist economy.

They viewed with great concern the rise of communism in the Soviet Union and in particular China, where the issue was fueling a civil war, and feared that the Soviet Union would make inroads in Asia by assisting China’s Communists.

The Japanese militarists thus found a common ideological enemy with Fascism and National Socialism, which had based their rise to power on anti-Communist sentiments. In 1936, Japan and Germany signed the Anti-Comintern Pact, pledging mutual assistance in defending themselves against the Comintern, the international agency created by the Soviet Union to promote worldwide Communist revolution. In 1937, Italy joined the pact, essentially creating the foundation of what became the military alliance of the Axis powers.

U.S. Embargo Efforts Against Japan Backfire

While Hitler marched across Europe, the Japanese continued their war in the Pacific. In 1939 the United States dissolved its trade treaties with Japan and the following year cut off supplies of war materials by embargoing oil, steel, rubber, and other vital goods. It was hoped that economic pressure would shut down the Japanese war machine. Instead, Japan’s resource-starved military launched invasions across the Pacific to sustain its war effort. The Japanese called their new empire the Greater East Asia Co-Prosperity Sphere and, with the cry of “Asia for the Asians,” made war against European powers and independent nations throughout the region. Diplomatic relations between Japan and the United States collapsed. The United States demanded that Japan withdraw from China; Japan considered the oil embargo a de facto declaration of war.