It's been six years since the events in Snake Eater. Snake has been captured and imprisoned in an abandoned missile silo in Colombia, and with no support this time. At least, not at first. With the help of a fellow prisoner, Snake escapes and the game truly begins.

Portable Ops is a classic Metal Gear game in almost every sense. The controls will be familiar to anyone who has played previous console entries in the series. Snake can peek around corners, sneak up behind guards, they even carried over the CQC moves from Snake Eater.

The main addition of Portable Ops is the Comrade System. Instead of the solo missions from previous games, Portable Ops uses a squad-based approach, with Snake having to recruit allies to form a team of trained specialists. Before each mission, the player must compose a four-man squad that will be sent into battle. Each member of Snake's squad has their own strengths and weaknesses. While some units are best utilized on the battlefield, others may specialize in producing items, healing allies, or providing intel for each of the game's maps.

Portable Ops has always been a controversial game among the fans due to its unconfirmed canonicity in the series, even Hideo Kojima himself hasn't be able to provide a clear answer in the matter. This has lead to extensive debates and theories if the game truly belongs to the Metal Gear main timeline.