 This change in policy came at a time when Japan was in the midst of a severe economic crisis from the Great Kantō earthquake and successive economic depressions, and caused both alarm and irritation in the Kwantung Army leadership.The situation was further complicated by the success of the Northern Expedition led by Chiang Kai-shek of the National Revolutionary Army, in which the Kuomintang successively defeated Sun Chuanfang, Wu Peifu and other warlords of the Northern Faction, as well as the Beijing government controlled by Zhang Zuolin.The Nationalist army appeared poised to restore its rule over Manchuria, which was still officially claimed as part of the Republic of China.