Second Sino-Japanese War

China and Japan fought the Second Sino-Japanese War from 7 July 1937 to Japan's surrender on 2 September 1945, after years of lower-level conflict that began with Japan's seizure of Manchuria in 1931. Known in China as the War of Resistance Against Japan, it was the largest Asian war of the twentieth century and is often seen as the start of the Second World War in Asia. Around 20 million people died, most of them Chinese civilians.

On 18 September 1931 Japanese officers staged the Mukden incident, a fabricated attack used as a pretext to occupy Manchuria, where Japan set up the puppet state of Manchukuo. Clashes followed over the next six years, in Shanghai and in northern China. China itself was divided: since 1927 the Nationalists under Chiang Kai-shek had been fighting the Communists led by Mao Zedong. Under the growing Japanese threat, and hastened by the Xi'an Incident, the two sides agreed in 1936 to form a United Front.

Full-scale war began after a clash at the Marco Polo Bridge near Beijing on 7 July 1937, which escalated into a Japanese invasion of the rest of China.

Fighting spread to Shanghai in August 1937. The long and costly battle there cost Chiang many of his best-trained troops. Japanese forces then advanced on the capital, Nanjing, captured it in December 1937 and carried out the Nanjing Massacre. Chinese forces won notable victories in 1938, including Taierzhuang in March and April, but could not prevent the loss of Wuhan, the wartime centre of government. The Nationalist government withdrew deep into the interior to Chongqing.

By 1939, with Japanese supply lines stretched far inland and after Chinese successes at Changsha, the war settled into a stalemate. Japan could not defeat the Communist forces based in Shaanxi, which waged a campaign of sabotage and guerrilla warfare. The Soviet Union sent aid until its neutrality pact with Japan in April 1941. In 1940 the Communists launched the Hundred Regiments Offensive; in reprisal Japanese forces carried out scorched-earth campaigns, including the "Three Alls" policy of "kill all, loot all, burn all", that killed very large numbers of civilians in northern and central China.

In December 1941 Japan attacked the United States at Pearl Harbor and declared war on the United States and Britain, joining the Chinese conflict to the wider Second World War. The United States became China's main supplier of money and arms. After Japan cut the Burma Road, supplies were flown over the Himalayas, and Chinese troops fought alongside British Empire forces in Burma. In 1944 Japan launched Operation Ichi-Go, invading Henan and the Changsha region, but in 1945 Chinese forces counter-attacked in the south and reopened a land route from India.

The war was marked by widespread atrocities against Chinese civilians. Japan carried out the largest biological warfare attacks in history, which are estimated to have killed at least 200,000 people, and also used chemical weapons. Many women, by some estimates more than 200,000, were forced into sexual slavery for the Japanese military as so-called comfort women. Estimates of total Chinese deaths range from about 10 million to 20 million, and Chinese figures for total casualties reach 35 million.

Japan surrendered after the atomic bombings of Hiroshima and Nagasaki and the Soviet invasion of Manchuria. The surrender of Japanese forces in China was signed at Nanjing on 9 September 1945. China, counted among the "Big Four" Allied powers, regained Taiwan and became a permanent member of the United Nations Security Council. But the truce between Nationalists and Communists did not last: the Chinese Civil War resumed in 1946 and ended in 1949 with the Communist victory and the Nationalist government's retreat to Taiwan.

Our 1938 map shows the Republic of China in the first year of full-scale war, and the 1945 map shows East Asia at the war's end.