The Kempeitai was the military police of the Imperial Japanese Army from 1881 to 1945. The organization also shared civilian secret police, espionage, and counter-intelligence roles within Japan and its occupied territories, and was notorious for its brutality and role in suppressing dissent. The broad duties of the Kempeitai included maintaining military discipline, enforcing conscription laws, protecting vital military zones, and investigating crimes among soldiers. In occupied areas, it also issued travel permits, recruited labor, arrested resistance, requisitioned food and supplies, spread propaganda, and suppressed anti-Japanese sentiment. At its peak at the end of World War II, the Kempeitai was an extensive corps with about 35,000 personnel.
Founded as a small corps during the Meiji era, the size and duties of the Kempeitai grew as Japanese militarism expanded. In World War II, the organization ran Japan's prisoner of war (PoW) and civilian internment camps, known for their mistreatment of detainees, and also acted as a political police force in the military and occupied territories. It carried out torture, summary executions, and violent reprisals and massacres against civilians, as well as procuring comfort women and human test subjects for Unit 731. It was disbanded after the war, and many of its leaders were tried and convicted of war crimes.
While institutionally part of the Army, the Kempeitai also discharged limited military police functions for the Imperial Japanese Navy. A member of the Kempeitai corps was called a kempei (憲兵).
The Kempeitai was established on 4 January 1881, during the Meiji era, by order of the Great Council of State as part of a broader modernization and Westernization of the Japanese military. Initially, the organization was an elite corps of 349 men, and was tasked with the narrow role of enforcing the new army conscription legislation.