Metal Gear Solid: Portable Ops was released in 2006. It takes place in 1970. It was released on the PlayStation Portable and was the first Metal Gear game on that platform to not be a Spin-Off; instead it forms part of the series' canon.
In 1970, six years after the events of Snake Eater, Naked Snake's former team, FOX unit, has broken their allegiance with the CIA and gone rogue. Snake is also targeted by the FOX unit, which has sent renegade FOX unit soldiers to capture him. The game begins with the torture and interrogation of Snake by one of the FOX members, Lieutenant Cunningham. Lt. Cunningham is trying to locate the missing half of the Philosopher's Legacy, with the United States Government having already acquired the other half of the Legacy from the Soviet Union at the conclusion of Snake Eater. 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. Snake learns through Roy that they are on the San Hieronymo Peninsula (a Russian transliteration of "San Jerónimo Peninsula") or "La PenÃnsula de los Muertos", the site of an abandoned Soviet missile silo in Colombia.
The two escape and Snake makes his way to a communications base, where he attempts to contact his old CO, Major Zero. Instead, he is greeted by his old FOX comrades Para-Medic and Sigint, who reveal that Snake and Zero are being charged for treason and that the only way for Snake to be exonerated from the charges is to find and apprehend the leader of the rebellion, Gene. To complicate matters, Gene has also convinced most of the Soviet soldiers stationed at the base to join their side by simply taking over the chain of command belonging to a Soviet unit which was secretly stationed inside the Colombian territory. In order to complete his mission, Snake must persuade enemy soldiers to join his ranks due to the scale of his mission.
Snake and his squad defeat the top members of the FOX unit and eventually they make their way into Gene's guesthouse. Snake learns many things on his way. 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. Gene was actually aware of this plan from the beginning due to information from Ocelot. Gene really wanted to launch a nuke at America to destroy the Philosophers and to make his nation of soldiers, "Army's Heaven". Snake destroys an experimental model of the ICBMG (the Metal Gear model) codenamed RAXA and eventually defeats Gene, destroying the finished ICBMG model afterward. After Gene is defeated he gives Snake the funds, equipment, personnel, and all other information regarding "Army's Heaven". On his return home, Snake is awarded for his actions, he then establishes FOXHOUND afterwards. Elsewhere, Ocelot kills the DCI (Director of Central Intelligence) and takes documents containing the identities of the Philosophers in an effort to "end them".
In the post-credits epilogue, Ocelot speaks with an unknown man on the phone, they are plotting to use the Legacy to fulfill their own agenda. Ocelot actually wanted the trajectory data of the nuke to point to the DCI, in order to blackmail the DCI into giving Ocelot the documents containing the true identities of the Philosophers. Ocelot agrees to join his new employer's project under the condition that Snake/Big Boss participates as well.
