The Akamatsu, Isshiki, Kyogoku and Yamana clans, whose heads were feudal lords that ruled local territories as military governors, were known as the "Shishiki (or Shishoku)" clans (meaning "four top ranking clans") and the military police director (called "tonin" or "shoshi" in Japanese) of the Muromachi bakufu (Japanese feudal government headed by a shogun) was chosen from among these clans in turn in order to take charge of military leadership, law enforcement and tax collection in the city of Kyoto.
室町幕府の軍事指揮と京都市中の警察・徴税等を司る侍所の長官（頭人、所司）に交代で任じられた守護大名の赤松氏、一色氏、京極氏、山名氏の4氏を指して「四職」と称する。