ANBU

Base of Operations: Hidden Village
Classification: Specialized Ninja Squad
Member Appearances: Uchiha Itachi, Hatake Kakashi, Uzuki Yuugao

The ANBU, meaning "dark side" is actually short for Ansatsu Senjutsu Tokushu Butai (literally Assassination Tactics Special Military Force). The ANBU work directly under the leadership of the Hokage. This specialized ninja battalion generally work in groups of four to five. They are responsible for assassinations and missions requiring highly trained ninjas. The masks the members wear are based around the signs of the zodiac.

Both Hatake Kakashi and Uchiha Itachi became ANBU at a young age. Itachi himself was said to have become an ANBU captain by age 13.