The Japanese title of Band of Assassins was Shinsengumi, which pinpointed the assassins in question. The Shinshen was a covert military organization in the employ of the 19th-century Japanese aristocracy. To protect their decadent employers, the Shinshen regularly ventured out to kill political enemies and other undesirables. Toshiro Mifune is among the participants in the film's steady (and seemingly endless) stream of bloodletting. Band of Assassins was one of the bread-and-butter pictures which Mifune made in order to afford to work in more prestigious fare.
by Hal Erickson synopsis