Retcon

Retroactive continuity, or retcon for short, is the alteration of previously established facts in the continuity of a fictional work.

Retcons are present in the Metal Gear series due to the instance of multiple writers, game planning revisions, and prequel creation. This ranges from character backgrounds, plot details, scientific explanations, and much more.

Metal Gear 2: Solid Snake

 * The MSX2 user's manual for Metal Gear implied that Operation Intrude N313 was Solid Snake's first experience on the battlefield. This was retconned when it was established that FOXHOUND would only pick recruits who had previous experience within the military. Later games would reveal that Snake had participated in the Gulf War as a Green Beret.

Metal Gear Solid

 * Solid Snake is an American of Japanese descent, and an operative of the U.S. Army special forces unit FOXHOUND. He was previously described as Japanese-British, under a NATO-led FOXHOUND, in the Metal Gear 2 user's manual.


 * Not in the game itself, but the manual for the game revealed that Big Boss had actually been the founder of FOXHOUND, instead of nominated as commander as previously indicated in the Metal Gear 2 manual. It was further retconned in Metal Gear Solid 3.


 * Sometime prior to his death in Metal Gear 2, Big Boss had informed Snake that he was his father. Snake later learns that he and Liquid Snake are actually clones of Big Boss, created in the Les Enfants Terribles project.


 * The global setting during the Zanzibar Land Disturbance is retconned to mirror real-world developments since the release of Metal Gear 2: nuclear weapons were not completely abandoned in the 1990s; the Soviet Union and Communist Bloc collapsed as it did in reality; CIS forces, formed around Russia, fought Zanzibar Land in the Mercenary War, rather than interventions from both East and West; Gustava Heffner was a former member of the Czech Secret Police rather than an active one.


 * Although not in the main game, the Metal Gear 2 section of the Previous Operations menu implied that Zanzibar Land had both been pursuing a nuclear weapons development program, and that the rest of the world had not been aware of their possessing nukes until after Kio Marv was captured by Zanzibar Land forces, contradicting both the Metal Gear 2 manual as well as the game itself's statements that Zanzibar Land had been stealing nukes from disposal facilities, as well as the west being aware of this since at least 1997.


 * Gray Fox is now the only FOXHOUND member to have ever attained the "Fox" title. It was previously stated that he was the last one to have done so under Big Boss's command.


 * Master Miller is depicted as having blond hair and wearing aviator sunglassess. He was originally depicted as an Asian looking man with black hair.

Metal Gear Solid 2: Sons of Liberty

 * Adding to the retcon established in Metal Gear Solid regarding the plotline in Metal Gear 2 about nuclear weapons being completely dismantled, a speech given by Scott Dolph during the Tanker Chapter established that then-President George Sears (Solidus Snake) had pushed for the NMD program to be completed, and the Plant Chapter also accredited James Johnson for its further success, and even the development of a purified hydrogen bomb.


 * Although not in the main game itself, Nastasha Romanenko's novel In the Darkness of Shadow Moses: The Unofficial Truth revealed that the Patriots had actually been responsible for Jim Houseman's arrest, something that Roy Campbell had previously been attributed to.

Metal Gear Solid 3: Snake Eater

 * The loss of Big Boss's eye occurs during the game, which is set in 1964, rather than the 1980s, as previously claimed in the Metal Gear 2 user's manual. The injury did not force him to retire from the front line, as it did in the former account.
 * Big Boss's sterility was established to have been caused by radiation from nuclear testing on the Marshall Islands. Earlier sources, including the Japanese version of Metal Gear Solid, implied that he had become sterile due to injuries sustained in direct combat.
 * Not in Metal Gear Solid 3 itself, but the port for Metal Gear and Metal Gear 2 included in Metal Gear Solid 3: Subsistence changed the names of several characters in the game.
 * FOXHOUND was established to have been founded in 1971, while the Metal Gear 2 and Metal Gear Solid manuals had earlier stated that it was founded during the 1990s. This retcon apparently had been a last minute addition, as the leaked Metal Gear Solid 3 voice casting sheet mentioned that FOXHOUND was founded in the 1990s. Because of this, Big Boss's motivation for founding FOXHOUND was further retconned from Metal Gear Solid, revealing he formed it to replace the FOX Unit, instead of due to being impressed with the effectiveness of high-tech weaponry during the Gulf War.

Metal Gear Solid: Portable Ops

 * Frank Jaeger's past was retconned, adding in another confrontation between him and Big Boss in Mozambique, and detailing his involvement in the San Hieronymo Takeover.


 * Nikolai Stephanovich Sokolov's apparent death during Operation Snake Eater was expunged, having instead survived with the aid a fake death pill from The Boss.


 * Gene revealed that the CIA had other motives for killing The Boss during Operation Snake Eater, which Big Mama later confirmed in Metal Gear Solid 4.


 * The Patriots usurped the power away from the American branch of the Philosophers. In the ending timeline of Metal Gear Solid 3, it was stated that the Patriots were a direct continuation of the American Philosophers under a different name.


 * In Metal Gear Solid 3, it is heavily implied that the CIA Director was the founder of the Patriots, using the Philosophers' Legacy he received from Ocelot to achieve this goal. In Portable Ops, he was killed by Ocelot. After killing the CIA Director, Ocelot stole the Philosophers' Legacy for his mysterious benefactor (who was confirmed to be Major Zero in Metal Gear Solid 4).


 * Although it is only in an optional mission, Ivan Raidenovitch Raikov was revealed to have survived Metal Gear Solid 3. The latter game had earlier left it ambiguous as to whether Raikov was killed or simply knocked out by Naked Snake.


 * Metal Gear Solid: Portable Ops itself has a shaky place in the canon, as it is not present in certain official timelines and the game's story was not written by Hideo Kojima. Kojima himself, however, confirmed in an interview that while the main story of the game is canon, specific details present in the game are not to be considered canon if they interfere with future entries in the series.

Metal Gear Solid 4: Guns of the Patriots

 * The founders of the Patriots are revealed to be many of the main characters from Metal Gear Solid 3, including Big Boss. Zero is confirmed to be Ocelot's mysterious benefactor from Portable Ops.


 * Implied at the end of Metal Gear Solid 3, Donald Anderson and Sigint are confirmed to be the same person.


 * Para-Medic is revealed to be Dr. Clark, the person responsible for Gray Fox's cybernetic augmentation, despite being referred to as a male in Metal Gear Solid. She is also revealed to have been responsible for the Les Enfants Terribles project, something that had only been implied in an optional radio conversation in Metal Gear Solid 3.


 * Drago Pettrovich Madnar survived the events of Metal Gear 2 and is revealed to have been living in Eastern Europe. In previous sources, it was strongly implied that Solid Snake had killed Dr. Madnar.


 * Some of Vamp's "superhuman" abilities are explained by the use of advanced technologies, including nanomachines.


 * Adding to the retcon established in Portable Ops, EVA revealed that The Boss had been eliminated by the CIA, as they had feared her charisma.


 * Rosemary remarks that Roy Campbell had actually been Raiden's commanding officer, even though Campbell was revealed to have still been in retirement in Metal Gear Solid 2.


 * Liquid's control over Ocelot through the transplanted arm, was revealed to have been an elaborate ruse by Ocelot accomplished with nanomachines and hypnotherapy.


 * Though not in the game itself, the supplemental Metal Gear Solid 4 Database inferred that Ocelot's affiliation with the SVR and OMO, mentioned by Naomi Hunter in Metal Gear Solid during the boss battle against him, had in fact been falsified to cover up his Patriot-related activities.

Metal Gear Solid: Peace Walker

 * McDonnell Benedict Miller's birth name is revealed to be Kazuhira, born in Japan to a Japanese mother and American father. In his previous backstory, he was born a third generation Japanese-American in the United States, 60 years after his Japanese grandparents immigrated to America.


 * In addition, Miller was also revealed in the secret tape to have been aware of the Les Enfants Terribles project and Big Boss's role in it, more specifically Solid and Liquid Snake's existence. It was previously stated in Metal Gear Solid that the only ones aware of Solid Snake's familial ties to Big Boss were Solid Snake himself and Roy Campbell.
 * Big Boss is revealed to have been 37 years old when the Les Enfants Terribles project took place, making him two decades younger than previously claimed by Liquid Ocelot in MGS2.


 * The Boss's past, including the reasons why The Sorrow and The Boss fought each other, was expanded upon in several data files, both from Strangelove and from EVA. In addition, her previous claim about having participated in the Bay of Pigs Invasion was retconned in the same game, as it revealed that she actually had been in a coma during that time from an accident relating to the Mercury Project.

Metal Gear Solid V: Ground Zeroes

 * During some optional radio calls in the main mission, Miller will call in stating that he couldn't believe he bought Paz Ortega Andrade's cover story, implying that he had similarly been duped by Paz's arrival in Colombia, when both the second ending of Metal Gear Solid: Peace Walker and the secret tapes earlier revealed that he had in fact been aware of her deception from the start, and in the case of the latter, was also in contact with Cipher.