The movie was directed by Kenji Fukusaku, one of the great Japanese directors. He fought in WW2 and made over 50 films in his career, including the infamous series "Battle without honor or humanity" a 6 part yakuza epic often called the Japanese Godfather. I used that film series as a basis for my yakuza games. It starts Beat Takeshi, one of the great grizzled actors of Japan.
The movie is fucking epic and it is by far the superior version of the story. I've read the novel and some of the manga and they don't have the same impact as the movie.