Still a battalion commander at the time of the Mukden Incident in 1931, Wang was stationed near Yanji, a small town in the east of Jilin province, where the Japanese were constructing a new, railway line.
When on February 8, 1932, Wang Delin proclaimed the establishment of the Chinese People's National Salvation Army (NSA), his battalion of 200 men had swollen to a force of over 1,000.
In March 1932, a Japanese and Manchukuoan expeditionary force was defeated in a series of battles with the NSA around the shore of Lake Jingpo losing hundreds of casualties.
By this time Wang had about 10,000 men and he was recognized as a general by the "Old Jilin" leader Gen. Li Du at his headquarters at Sanxing in Heilongjiang Province on the lower Sungari River.
The Japanese had concentrated northwest of Harbin against General Ma Zhanshan in spring and summer of 1932, which allowed the increase in partisan activity in Jilin and Liaoning provinces.
This activity culminated in simultaneous attacks on cities throughout the South Manchurian Railway Zone as severe August floods halted Japanese operations based on Harbin, and isolated the troops engaged on them.
The Japanese followed up with "Anti Bandit" Operations that fall and winter that eventually drove the Volunteer armies to break up into small bands or retreat into the Soviet Union as Wang's force did on January 13, 1933.