 He moved to Shanxi, where his men were reorganized as 40th Division and garrisoned at Jincheng.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.