Anbu

The Anbu (暗部; English TV "Anbu Black Ops"; Literally meaning "Dark Side"), short for Ansatsu Senjutsu Tokushu Butai (暗殺戦術特殊部隊; Literally meaning "Special Assassination and Tactical Squad"), take orders directly from the Kage, performing special high-level missions, such as assassinations and torture. The Anbu usually work in teams formed to the requirements of the mission, ensuring maximum success. The shinobi in the Anbu are hand-picked by the Kage, chosen for their individual capabilities and special skills. Age, gender, background, or previous rank bear no weight in this decision. Members can be relieved from the Anbu by the Hokage and reassigned elsewhere, in Kakashi's case, he was reassigned by Hiruzen Sarutobi from the Anbu to the regular forces as a jōnin leader.[2] They wear their mask even in their own village, for their identity as an Anbu agent is to be known only by the Kage and village elders, with the exception of Konohagakure's "Root" Anbu members who, unless ordered to, will only act on Danzō Shimura's orders.

There are apparently no true ranks within the Anbu, unlike within the regular forces. Team leadership and hierarchy seem to be based on merit and experience. The leaders of the teams are called squad leaders (分隊長, Buntaichō), a position held in high regard.