The Kempeitai (also spelled Kenpeitai) was the military police arm of the Imperial Japanese Army and was formed in 1881. It was modelled after the Gendarmerie of France (a military component with jurisdiction in civil law enforcement). The Kempeitai operated as both a military police body as well as a secret police force.

On the Japanese mainland the Kempeitai operated under the direction of the Interior Ministry, primarily to maintain public order. When operating in conquered territories prior to the end of WWII, it operated under the Ministry of War for maintaining public order, functioning as a military police force and gathering intelligence. It operated a branch referred to as "Tokkō" that served as a secret police force.

The Kempeitai's brutality was particularly notorious in Korea and the other occupied territories. The Kempeitai were also abhorred in the Japanese mainland as well, especially during World War II when Prime Minister Hideki Tojo, a former Commander of the Kempeitai in Manchuria from 1935 to 1937, used the Kempeitai to ensure Japanese citizens were loyal to the war effort.

The Kempeitai was disbanded after Japan's surrender in August 1945.

More Info: en.wikipedia.org