The entire cast of Hell in the Pacific consists of two high-powered international stars: Lee Marvin and Toshiro Mifune. The time is World War II. A downed American marine pilot (Marvin), is stalked on a remote Pacific island by a Japanese navy officer (Mifune). The Japanese officer captures the American, but this situation is reversed when he manages to wriggle free. The two enemies finally decide to live and let live, each moving to their own separate portion of the island. By and by the adversaries come to rely upon one another to survive; they set up living quarters in a deserted camp, get drunk together, and almost -- but not quite -- become friends. The present ending of Hell in the Pacific is greatly at odds with director John Boorman's original vision, in which the Japanese officer angrily kills two Japanese soldiers who have come across the American and decapitated him. As it now stands, viewers are left with an explosive "lady or the tiger" denouement.
~ Hal Erickson, All Movie Guide