This is a study of the role played by Ch'en Ch'eng, who for almost thirty years was Chiang Kai-shek's most trusted and powerful lieutenant, in the relations between Chiang's “Central” government and the so-called tsa-parh or noncentral military forces. The study illustrates both the complexity and importance of Chiang's dealings with the tsa-parh and suggests that Ch'en had the responsibility of coopting them into Chiang's service. This was especially true with respect to militarists from Kwangtung and Kwangsi, who felt that their leadership of the Nationalist movement had been usurped by the Chekiang-Kiangsu group, led by Chiang Kai-shek. Ch'en also emerges as an advocate of fundamental social and economic reform, as well as an important proponent of resisting Japan and, therefore, the united front with the Communists, although, after 1945, he became chief-of-staff to Chiang Kai-shek and, in this capacity, directed Nationalist efforts to destroy the Communists. The article concludes by suggesting that Nationalist efforts to impose a “modern,” meaning a unitary and organically centralized, state on what traditionally had been a politically fragmented society provoked unprecedented antagonism toward the central government on the part of the provinces and prevented Chiang Kai-shek from achieving even that degree of control enjoyed by China's emperors in the past.