 In early 1933, the Imperial Japanese Army launched Operation Nekka to conquer Jehol Province.At the time, Sun commanded the 41st Army of 30,000 men, most of them garrisoned in Lingyuan; one of the soldiers under his command during this conflict was writer Duanmu Hongliang.As the Japanese closed in on Lingyuan, Sun did not resist, as he and his sub-commanders had been bribed by the invaders.