P.T.O.: Pacific Theater of Operations, or Teitoku no Ketsudan ("Admiral's Decision"), is a Koei strategy series based on the Pacific Theater of World War II. The player assumes the role of admiral, maintaining the fleets and naval bases of their chosen side (either the US or Japan) and working with other countries, Allied or Axis, to procure resources and ships through diplomacy.
The series began on home computers before being ported to 16-bit systems, with the most recent being the PS2 game P.T.O. IV. All but the third game in the series, Teitoku no Ketsudan III (which released on Saturn and PS1), was localized for the west.