World War II in Asia

Japan's invasion of China began the war in the Pacific theater

Chinese Training
Chinese Nationalist troops, 1944. Keystone / Getty Images

Most historians date the beginning of World War II to September 1, 1939, when Nazi Germany invaded Poland. Others claim the war began on July 7, 1937, when the Japanese Empire invaded China. From the Marco Polo Bridge Incident of July 7 to the eventual surrender of Japan on August 15, 1945, the Second World War ravaged Asia and Europe alike, with bloodshed and bombardment spreading as far as Hawaii.

1937: Japan Invades China

On July 7, 1937, the Second Sino-Japanese War began with a conflict known as the Marco Polo Bridge Incident. Japan was attacked by Chinese troops while carrying out military training—they didn't warn the Chinese they would be shooting gunpowder rounds at the bridge that led to Beijing. This amplified already tense relations in the region, leading to an all-out declaration of war.

In July of that year, the Japanese launched their first assault with the Battle of Beijing at Tianjin, before marching to the Battle of Shanghai on August 13. The Japanese won huge victories and claimed both cities for Japan, but suffered heavy losses. Meanwhile, in August of that year, the Soviets invaded Xinjiang in western China to put down the Uighur uprising.

Japan launched another military assault at the Battle of Taiyuan, claiming the capital of Shanxi Province and China's arsenal of weapons. From December 9 to 13, the Battle of Nanking resulted in the Chinese provisional capital falling to the Japanese and the Republic of China government fleeing to Wuhan.

From the middle of December 1937 to the end of January 1938, Japan furthered tensions in the region by taking part in a month-long siege of Nanjing, killing approximately 300,000 civilians in an event that came to be known as the Nanking Massacre or the Rape of Nanking (after the raping, looting, and murder the Japanese troops committed).

1938: Increased Japan-China Hostilities

The Japanese Imperial Army had begun to take on its own doctrine by this point, ignoring orders from Tokyo to halt southward expansion in the winter and spring of 1938. On February 18 of that year, they launched the Bombing of Chongqing, a years-long firebombing against the Chinese provisional capital, killing 10,000 civilians.

Fought from March 24 to May 1, 1938, the Battle of Xuzhou resulted in Japan capturing the city but losing the Chinese troops, who would later become guerrilla fighters against them, breaking dams along the Yellow River in June of that year, halting Japanese advances but also drowning Chinese civilians.

In Wuhan, where the ROC government had relocated the year before, China defended its new capital at the Battle of Wuhan but lost to 350,000 Japanese troops, who only lost 100,000 of their men. In February, Japan seized the strategic Hainan Island and launched the Battle of Nanchang—which broke Chinese National Revolutionary Army's supply lines and threatened all of southeast China—as part of an effort to stop foreign aid to China.

However, when they attempted to take on the Mongols and Soviet forces in the Battle of Lake Khasan in Manchuria and the Battle of Khalkhyn Gol along the border of Mongolia and Manchuria in 1939, Japan suffered losses.

1939 to 1940: Turning of the Tide

China celebrated its first victory on October 8, 1939. At the First Battle of Changsha, Japan attacked the capital of the Hunan Province, but the Chinese army cut Japanese supply lines and defeated the Imperial Army.

Still, Japan captured the Nanning and Guangxi coast and stopped foreign aid by sea to China after winning the Battle of South Guangxi. China wouldn't go down easy, though, and launched the Winter Offensive in November 1939, a country-wide counteroffensive against Japanese troops. Japan held in most places, but they realized then it would not be easy to win against China's sheer size.

Although China held onto the critical Kunlun Pass in Guangxi that same winter, keeping a supply flow from French Indochina to the Chinese army, the Battle of Zoayang-Yichang saw Japan's success in driving toward the provisional new capital of China at Chongqing.

Firing back, Communist Chinese troops in northern China blew up rail-lines, disrupted Japanese coal supplies, and even made a frontal assault on Imperial Army troops, resulting in a strategic Chinese victory in December 1940.

As a result, on December 27, 1940, Imperial Japan signed the Tripartite Pact, which aligned the nation with Nazi Germany and Fascist Italy as part of the Axis Powers.

1941: Axis Versus Allies

As early as April 1941, volunteer American pilots called the Flying Tigers begin to fly supplies to Chinese forces from Burma over "the Hump"—the eastern end of the Himalayas, and in June of that year, combined British, Indian, Australian, and Free French troops invaded Syria and Lebanon, held by pro-German Vichy French, who surrendered on July 14.

In August 1941, the United States, which had supplied 80 percent of Japan's oil, initiated a total oil embargo, forcing Japan to seek new sources to fuel its war effort, and the September 17 Anglo-Soviet Invasion of Iran complicated the matter by deposing the pro-Axis Shah Reza Pahlavi and replacing him with his 22-year-old son to ensure the Allies' access to Iranian oil.

The end of 1941 saw an implosion of the Second World War, starting with the December 7 Japanese attack on the U.S. Navy base at Pearl Harbor, Hawaii, which killed 2,400 American service members and sank four battleships. Simultaneously, Japan initiated the Southern Expansion, launching a massive invasion aimed at the Philippines, Guam, Wake Island, Malaya, Hong Kong, Thailand, and Midway Island. 

In response, the United States and the United Kingdom formally declared war on Japan on December 8, 1941. Two days later, Japan sank the British warships H.M.S. Repulse and H.M.S. Prince of Whales off the coast of Malaya, and the U.S. base at Guam surrendered to Japan. 

Japan forced British colonial forces in Malaya to withdraw up to the Perak River a week later and from December 22 to 23, launched a major invasion of Luzon in the Phillippines, forcing American and Filipino troops to withdraw to Bataan.

1942: More Allies and More Enemies

By the end of February 1942, Japan had continued its assault on Asia, invading the Dutch East Indies (Indonesia), capturing Kuala Lumpur (Malaya), the islands of Java and Bali, and British Singapore, and attacking Burma, Sumatra, and Darwin (Australia)—the beginning of Australia's involvement in the war.

In March and April, the Japanese pushed into central Burma—a "crown jewel" of British India—and raided the British colony of Ceylon in modern-day Sri Lanka. Meanwhile, American and Filipino troops surrendered at Bataan, resulting in Japan's Bataan Death March. At the same time, the United States launched the Doolittle Raid, the first bombing raid against Tokyo and other parts of the Japanese home islands.

From May 4 to 8, 1942, Australian and American naval forces fended off the Japanese invasion of New Guinea at the Battle of the Coral Sea. At the battle of Corregidor, however, the Japanese took the island in Manila Bay, completing its conquest of the Philippines. On May 20, the British finished withdrawing from Burma, handing Japan another victory.

At the pivotal June 4 to 7 Battle of Midway, American troops maneuvered a huge naval victory over Japan at Midway Atoll, west of Hawaii, and Japan quickly fired back by invading Alaska's Aleutian Island chain. In August of that same year, the Battle of Savo Island saw the United States' first major naval action and the Battle of the Eastern Solomon Islands, an Allied naval victory, in the Guadalcanal campaign.

1943: A Shift in the Allies' Favor

From December 1942 to February 1943, the Axis powers and the Allies played a constant tug-of-war, but supplies and munitions were running low for Japan's already thinly spread troops. The United Kingdom capitalized on this weakness and launched a counter-offensive against the Japanese in Burma.

In May 1943, China's National Revolutionary Army made a resurgence, launching an offensive along the Yangtze River, and in September Australian troops captured Lae, New Guinea, claiming the region back for Allied powers—and shifting the tide for all of its forces to begin the counter-offensive that would shape the rest of the war.

By 1944, the tide of war was turning and the Axis Powers, including Japan, were at a stalemate or even on the defensive in many places. The Japanese military found itself over-extended and out-gunned, but many Japanese soldiers and ordinary citizens believed that they were fated to win. Any other outcome was unthinkable.

1944: Allied Domination

Continuing from its success along the Yangtze River, China launched another major offensive in northern Burma in January 1944 in an attempt to reclaim its supply line along the Ledo Road into China. The next month, Japan launched the Second Arakan Offensive in Burma, attempting to drive the Chinese forces back—but they failed.

The United States took Truk Atoll, Micronesia, and Eniwetok in February and halted Japanese advancement at Tamu, India, in March. After suffering a defeat at the Battle of Kohima, the Japanese forces retreated back into Burma, also losing the Battle of Saipan in the Marian Islands later that month.

The biggest blows, though, were yet to come. Starting with the Battle of the Philippine Sea, in July 1944, a key naval battle that effectively wiped out the Japanese Imperial Navy's carrier fleet, the United States began to push back against Japan in the Philippines. By December 31, Americans had mostly succeeded in liberating the Philippines from Japanese occupation.

Late 1944 to 1945: The Nuclear Option and Japan's Surrender

After suffering many losses, Japan refused to surrender to Allied parties—and thus the bombings started to intensify. With the advent of the nuclear bomb looming overhead and tensions continuing to mount between the rival armies of the Axis powers and the Allied forces, the Second World War came to its climax.

Japan upped its aerial forces in October 1944, launching its first kamikaze pilot attack against the U.S. Naval fleet at Leyte, and the United States answered back on November 24 with the first B-29 bombing raid against Tokyo.

In the first months of 1945, the United States continued to push into Japanese-controlled territories, landing on Luzon Island in the Philippines in January and winning the Battle of Iwo Jima in March. Meanwhile, the Allies reopened the Burma Road in February and forced the last Japanese to surrender in Manila on March 3.

When U.S. President Franklin Roosevelt died on April 12 and was succeeded by Harry S Truman, the bloody war ravaging Europe and Asia was already at its boiling point—but Japan refused to surrender.

On August 6, 1945, the American government decided to use the nuclear option, conducting atomic bombing of Hiroshima, Japan, the first nuclear strike of that size against any major city in any nation in the world. On August 9, just three days later, another atomic bombing was carried out against Nagasaki, Japan. Meanwhile, the Soviet Red Army invaded Japanese-held Manchuria.

Less than a week later, on August 15, 1945, the Japanese Emperor Hirohito formally surrendered to Allied troops, ending the Second World War.