HIS: This Day in History: 1945 – Second Sino-Japanese War: The Empire of Japan formally surrenders to China.

 HIS: This Day in History: 1945 – Second Sino-Japanese War: The Empire of Japan formally surrenders to China.

The Second Sino-Japanese War was a military conflict that was primarily waged between the Republic of China and the Empire of Japan from 7 July 1937 to 2 September 1945. The start of the war is typically considered to be the Marco Polo Bridge Incident in 1937, in which a dispute between Japanese and Chinese troops escalated into a full-scale invasion. Some sources in the modern People's Republic of China date the beginning of the war to the Japanese invasion of Manchuria in 1931. In China, it is known as the War of Resistance against Japanese Aggression.

China fought Japan with aid from the Soviet Union and the United States. After the Japanese attacks on Malaya and Pearl Harbor in 1941, the war merged with other conflicts of World War II as a major sector known as the China Burma India Theater. Some scholars consider the start of the full-scale Second Sino-Japanese War in 1937 to have been the beginning of World War II. The Second Sino-Japanese War was the largest Asian war in the 20th century. It accounted for the majority of civilian and military casualties in the Pacific War, with between 10 and 25 million Chinese civilians and over 4 million Chinese and Japanese military personnel missing or dying from war-related violence, famine, and other causes. The war has been called "the Asian holocaust."

The war was the result of a decades-long Japanese imperialist policy to expand its influence politically and militarily in order to secure access to raw material reserves, food, and labor. The period after World War I brought about increasing stress on the Japanese polity. Leftists sought universal suffrage and greater rights for workers. Increasing textile production from Chinese mills was adversely affecting Japanese production and the Great Depression brought about a large slowdown in exports. All of this contributed to militant nationalism, culminating in the rise to power of a militarist faction. This faction was led at its height by the Hideki Tojo cabinet of the Imperial Rule Assistance Association under edict from Emperor Hirohito. In 1931, the Mukden Incident helped spark the Japanese invasion of Manchuria. The Chinese were defeated and Japan created a new puppet state, Manchukuo; many historians cite 1931 as the beginning of the war. This view has been adopted by the PRC government. From 1931 to 1937, China and Japan continued to skirmish in small, localized engagements, so-called "incidents".

Following the Marco Polo Bridge Incident, the Japanese scored major victories, capturing Beijing, Shanghai and the Chinese capital of Nanjing in 1937, which resulted in the Rape of Nanjing. After failing to stop the Japanese in the Battle of Wuhan, the Chinese central government was relocated to Chongqing (Chungking) in the Chinese interior. By 1939, after Chinese victories in Changsha and Guangxi, and with Japan's lines of communications stretched deep into the Chinese interior, the war reached a stalemate. The Japanese were also unable to defeat the Chinese communist forces in Shaanxi, who waged a campaign of sabotage and guerrilla warfare against the invaders. While Japan ruled the large cities, they lacked sufficient manpower to control China's vast countryside. In November 1939, Chinese nationalist forces launched a large scale winter offensive, while in August 1940, Chinese communist forces launched a counteroffensive in central China. The United States strongly supported China. It began supplying military and financial aid, and cut off Japan's oil exports.

In December 1941, the United States declared war on Japan and increased its flow of aid to China. With Burma cut off it airlifted material over the Himalayas. In 1944, Japan launched the invasion, Operation Ichi-Go, that conquered Henan and Changsha. However, this failed to bring about the surrender of Chinese forces. In 1945, the Chinese Expeditionary Force resumed its advance in Burma and completed the Ledo Road linking India to China. At the same time, China launched large counteroffensives in South China and retook West Hunan and Guangxi. Japan formally surrendered on September 2, 1945. China regained all territories lost to Japan.