[1] The game was directed by Masahiro Yamamoto and written by Gakuto Mikumo, with series creator Hideo Kojima acting as producer.

[5] Portable Ops draws heavily from Metal Gear Solid 3: Snake Eater, utilizing the camera system from the Subsistence edition of the game.

[7] Instead of the solo missions of previous MGS games, MPO goes for a squad-based approach, with Snake having to recruit allies and form a team of trained specialists.

[12] Characters that can be recruited by the player include Soviet soldiers, FOX unit members, high-ranking officers, scientists, engineers and government officials.

[11][14] Similar to the radar in previous titles, the surround indicator allows players to determine the relative proximity of enemy soldiers by the noises they make.

[10] In contrast to the console games in the series, the cutscenes that drive the story are not rendered using the usual real time engine.

It follows the soldier Naked Snake (David Hayter/Akio Ōtsuka) who is forced to fight off his former unit, FOX, after they instigate a revolt in a South American base.

In his fight he meets Roy Campbell (David Agranov/Toshio Furukawa), a surviving member of the Green Berets team that was sent to investigate the affair.

The main antagonist is Gene (Steven Blum/Norio Wakamoto), the current commander of the FOX unit who seeks to establish his own military nation.

[21] (who is later revealed to be a double agent of the Pentagon sent to tarnish the CIA's reputation)[22] Gene also has a protégé named Elisa (Tara Strong/Saori Goto) who is gifted with extraordinary psychic abilities, implied to be the result of exposure to nuclear fallout during the Kyshtym disaster.

[2][23] Two FOX members previously associated with Snake include Null (Larc Spies/Jun Fukuyama), a teenage assassin trained to be the perfect soldier.

[26] Snake is imprisoned in a cell next to Roy Campbell, the sole survivor of an American Green Beret team sent in to investigate the base.

Cunningham was working for the Pentagon and wanted Snake to push Gene into launching a nuke at the Soviet Union to tarnish the CIA's reputation and to prolong the Cold War.

[30] The game was conceptualized when the Kojima Productions staff decided to make the first Metal Gear Solid chapter rather than another spin-off for the PlayStation Portable.

Some of the staff had previously worked in the spin-off Metal Gear Acid 2 making Portable Ops their first time doing a main installment.

Since players cannot spin the camera with the PlayStation Portable the game added a sound indicator system that helps them to see where there are enemies.

This would carry over with the promotion of the series' 20th Anniversary campaign, in which MPO was packaged alongside the three mainline MGS games at the time as part of a box set released in Japan,[33] and later on with the release of MGS4, in which the Metal Gear Solid 4: Database (a downloadable encyclopedia for the PS3 covering the lore of the Metal Gear series up to that point) include entries for characters, items and events depicted in MPO.

[35] MPO was, however, still included in the backstory of Big Boss and official Konami and Kojima Productions Metal Gear Saga timelines both before and after release.

[42][43] However, MPO was also still included in the expanded timelines outlining the backstory and history of mainline Metal Gear games and characters.

[51] In Japan, it was released two weeks later, on December 21, in two limited edition packages, with both of them sharing most of its unique bonus content, such as a special camouflage for the PlayStation Portable, as well as a set of three original lapel pins.

[53] In the United Kingdom, the game could only be released on May 25, 2007, after it was revealed that the required BBFC rating was missing, forcing retailers to send back their stocks.

[57] The musical score of Portable Ops was composed by Norihiko Hibino, Takahiro Izutani, Yoshitaka Suzuki, Kazuma Jinnouchi, Nobuko Toda and Akihiro Honda.

"Calling to the Night" was later featured in Metal Gear Solid 4: Guns of the Patriots as an iPod track, and Nintendo's Super Smash Bros. Brawl as one of the songs played on the Shadow Moses Island stage.

[citation needed] Metal Gear Solid: Portable Ops Plus (officially abbreviated MPO+) is a stand-alone expansion of the original MPO, focused primarily on online play.

MPO+ include new general and unique character types from other MGS titles, as well as new items and weapons, new multiplayer maps, and new game modes.