Originating from the local military organization of Ch'en Min, a strong man in Ch'ien-chou, the Tso-i Army was founded in 1148 when the Sung court was facing local rebellions in Fu-chien. According to the Sung court's planning, the Tso-i Army would be subordinated to both the Palace Command and the Military Commissioner of Fu-chien. The court hoped that, this way, the local armies would make the most of their military strength; it also wanted to avoid that local armies would be organized by private military power. At the same time, this represented is modification of the policy of "a strong trunk and weak branches" when confronted with internal and external threats. In the early stages, the headquarters of the Tso-i Army was set up in Fu-chou. In 1156 it was moved to Ch'uan-chou, and in 1235 it was temporarily transferred to Chien-ning Prefecture. In order to maintain public order, divisions of the Tso-i Army were also garrisoned in places like Chang-chou, Ting-chou and Fu-chou. The total number of men was about 5000. The costs of the Tso-i Army were born by various places in Fu-chien; the most important contributor was Ch'uan-chou where the general headquarters was located. Insufficiencies were, furthermore, made up for by the Sung court. Even though the main function of the Tso-i Army was to maintain local order in Fu-chien, the Sung court also used the pacification of rebellions and the resistance to foreign aggression as reasons to dispatch it to participate in military activities outside the region. For instance, in 1161 when Emperor Hailing of the Chin Dynasty invaded the south, during Chang Chun's northern expedition and during the northern campaign in the K'ai-hsi period, up to the revolt of the Storm Wind Tung (minorities in the south) and the rebellion of Ch'en San-ch'iang, in all these cases the Tso-i Army was sent out on military expeditions. This is a sign that the Sung court was exercising the power of command, this also sheds light on the characteristics of the central leadership. As a result, since the Tso-i Army had become an expeditionary army that could be moved acording to military orders, its original function of maintaining the public order in Fu-chien was rendered obscure. Especially after the northern expedition during the Kai-hsi reign, its real power was greatly affected due to the severe losses it had suffered. That it was now necessary to rely on the Huai Army for the pacification of rebellions within the borders of Fu-chien demonstrates that the military strength of the Tso-i Army was on the becline. Since Ch'uan-chou was the main financier of the Tso-i Army, it became possible for the prefect of Ch'uan-chou in 1221 to control the Tso-i Army. Afterwards, local power and the interests of local officials combined and created a community based on common destiny; its local character grew stronger and stronger. In the course of the Mongol destruction of the Sung, the local forces lead by P'u Shou-keng and the Tso-i Army, motivated by considerations of personal gain, and the scholar-officials, the dynastic house and the Huai Army, resisting the Yuan, differed greatly in their sympathies for the new or old political powers. P'u Shou-keng and others used the Tso-i Army to root out those groups with differing political convictions and surrendered to the new Mongol Yuan Dynasty. This is one example of how Southern Sung local armies took a realistic position to face the changing conditions.