Following Kammu's death in 806 and a succession struggle among his sons, two new offices were established in an effort to adjust the Taika-Taihō administrative structure. Through the new Emperor's Private Office, the emperor could issue administrative edicts more directly and with more self-assurance than before. The new Metropolitan Police Board replaced the largely ceremonial imperial guard units. While these two offices strengthened the emperor's position temporarily, soon they and other Chinese-style structures were bypassed in the developing state. In 838 the end of the imperial-sanctioned missions to Tang China, which had begun in 630, marked the effective end of Chinese influence. Tang China was in a state of decline, and Chinese Buddhists were severely persecuted, undermining Japanese respect for Chinese institutions. Japan began to turn inward.