Chiang's troops, however, continued to expand their control in northern China and the Japanese army's distrust of the forces of Chinese nationalism would only grow.[38] According to historian Akira Iriye, the Jinan incident demonstrated the weak nature of the Japanese chain of command, and the powerlessness of civilian government officials to stop unilateral aggression by the military.[39] Japanese army leaders, increasingly outside civilian control, feared that Chiang would respond to patriotic agitation and threaten their interests in southern Manchuria.[40] Following the precedent of General Fukuda's unilateral action in Jinan, a group of officers of the Kwantung Army assassinated the leader of the Beiyang government and ruler of Manchuria Zhang Zuolin on 4 June 1928, setting off a chain of events that created the pretext for the 1931 Japanese invasion of Manchuria.[41]