The centralized police system steadily acquired responsibilities, until it controlled almost all aspects of daily life, including fire prevention and mediation of labor disputes. The system regulated public health, business, factories, and construction, and it issued permits and licenses. The Peace Preservation Law of 1925 gave police the authority to arrest people for "wrong thoughts". Special Higher Police (Tokko) were created to regulate the content of motion pictures, political meetings, and election campaigns. The Imperial Japanese Army's military police (Kempeitai) and the Imperial Japanese Navy's Tokkeitai, operating under their respective services and the justice and home ministries aided the civilian police in limiting proscribed political activity. After the Manchurian Incident of 1931, military police assumed greater authority, leading to friction with their civilian counterparts. After 1937 police directed business activities for the war effort, mobilized labor, and controlled transportation.