In the 1930s, a song became popular all over China. The lyrics go, "September 18th, September 18th. On that tragic day, I was forced to leave my hometown ... " What happened on September 18th?

Since the late 19th century, Japan had unleashed multiple wars of aggression against China, and seized Taiwan. China was the chief objective of its full-fledged military expansion in 20th century. Three northeastern provinces of China became Japanese first target.

On the evening of September 18th, 1931, Japanese troops blew up part of a railway line at Liutiaohu, which is close to Shenyang. They then accused Chinese army of trying to launch an attack against Japan. Soon after, Japanese attacked the barracks of Northeast Army and the city of Shenyang. With massive casualties, the city was lost overnight.

At this time, National Government of the KMT was busy trying to eliminate the CPC. Chiang Kai-shek ordered Zhang Xueliang, leader of Northeast Army, should adopt the policy of nonresistance to avoid broadening the scope of the event. Without any Chinese army standing against them, Japanese army easily occupied the three provinces of nowtheast China, with a population of 30 million in only four months.

In order to consolidate their rule over northeast China, Japanese invaders established a puppet state called Manchukuo, with Puyi, the abdicated last emperor of Qing Dynasty as its puppet ruler within complete control of Japan. This aroused great indignation among local Chinese, who formed army volunteers to fight against invaders under extremely difficult circumstances.