Retroactive continuity, or retcon for short, is a new piece of information that imposes a different interpretation on previously described events. In regards to the Metal Gear series, a retcon is a situation in which the storyline of a new game explains or changes an event from a previous one, or attaches a new significance to it.
Retcons are typically used in the Metal Gear series to facilitate a dramatic plot shift or account for an inconsistency. Some retcons add information that contradicts the information that was previously established, while others instead fill in missing background details, allowing the accommodation of prequels/sequels or acknowledgement of real world developments. While creating the series, Hideo Kojima was willing to contradict established continuity on occasion, in order to ensure that "new games are as good as they can be."
Metal Gear 2: Solid Snake
- It is revealed that the game takes place in 1999, three years after the events of Metal Gear. In the original game, the year of its setting was unspecified (19XX).
- Kyle Schneider survived the events of Metal Gear and is revealed to have become a Zanzibar Land mercenary.
- Schneider explains that NATO destroyed Outer Heaven through a bombing campaign that was conducted following Snake's escape. Previously, it was heavily implied in the ending of Metal Gear that Outer Heaven was destroyed by the explosion that was activated as a result of the self-destruct sequence initiated by Big Boss.
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.
- Snake's IQ is stated to be 180. In the Metal Gear 2 manual, this figure was 160.
- 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.
- Snake states that Big Boss had informed him that he was his father. This never actually happens in Metal Gear 2.
- 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 they did in reality; the Commonwealth of Independent States (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 Dr. Kio Marv was captured by Zanzibar Land forces. This contradicts both the Metal Gear 2 manual and the game itself as it was stated that Zanzibar Land had been stealing nukes from disposal facilities, with 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. In addition, it is revealed that he survived the events of Metal Gear 2 and was turned into a cyborg. It was heavily implied in the previous game that Gray Fox died after fighting Solid Snake.
- When Snake discusses Gray Fox with Naomi Hunter, he states that "I learned a lot from him" and "he showed me the ropes" during the Outer Heaven Uprising. In Metal Gear, the liberated Gray Fox simply tells Snake what Metal Gear is and where Dr. Drago Pettrovich Madnar is located within Outer Heaven (with his directions turning out to be incorrect due to Madnar being moved just before Snake arrives at the location). Fox is neither seen nor mentioned again for the rest of the game. Additionally, such an interaction hardly implies the level of "friendship" that Snake ascribes it to be in Metal Gear Solid.
- Master Miller is depicted as having blond hair and wearing aviator sunglassess. He was originally depicted as an Asian looking man with black hair.
- The manual for Metal Gear 2 states that Operation Intrude F014 takes place in 1999. The Previous Operations summary, as well as subsequent sources, states that the game takes place four years after the events of Metal Gear. This contradicts Metal Gear 2, where Dr. Madnar and Snake state that three years had passed since the events of Metal Gear. This was due to the manual stating that the Outer Heaven Uprising occurred in 1995, while the first Metal Gear was developed a year later.
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.
- It is stated that Sergei Gurlukovich was leading a private mercenary group during Metal Gear Solid. Sergei was previously described as the "head of Spetsnaz."
- 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 late 1980s, as previously claimed in the Metal Gear 2 user's manual. The injury did not force him to retire from the frontline, 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, simply stated that he had become sterile due to injuries sustained in direct combat.
- Not in Metal Gear Solid 3 itself, but the ports for Metal Gear and Metal Gear 2 included in Metal Gear Solid 3: Subsistence changed the names of several characters in the games. In addition, all the character portraits were given new and/or updated designs by Yoji Shinkawa in the latter.
- FOXHOUND is 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. Big Boss's motivation for founding FOXHOUND was changed from the Metal Gear Solid manual's account, revealing that he formed it to replace the FOX Unit, rather than his 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, detailing his involvement in the San Hieronymo Incident. In addition, Jaeger was previously referred to as a child soldier by Naomi Hunter in Nastasha Romanenko's book when describing how he adopted her in the 1980s, but he is a teenager in Portable Ops.
- 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 claimed that a CIA strategist had deliberately manipulated Colonel Volgin into launching the Davy Crockett in Tselinoyarsk, thus ensuring The Boss's self-sacrifice.
- The Patriots usurped 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.
Metal Gear Solid 4: Guns of the Patriots
- Donald Anderson and Sigint are revealed 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.
- EVA is revealed to be the surrogate mother of Solid and Liquid Snake.
- Solid Snake's Japanese ancestry is explained to be the result of the donor eggs that were used in the Les Enfants Terribles project coming from Dr. Clark's assistant.
- The founders of the Patriots are revealed to be Naked Snake's support team from Operation Snake Eater and Ocelot.
- Dr. Madnar survived the events of Metal Gear 2 and is revealed to have been living in Eastern Europe. In previous sources, it was heavily implied that Solid Snake had killed him.
- Big Boss also survived the events of Metal Gear 2 and is revealed to have been placed in a nanomachine-induced coma for 15 years. Previous games had explicitly stated that Big Boss was killed during his fight with Solid Snake.
- Solidus Snake is revealed to have become brain dead as a result of his fight with Raiden. His clinical death occurs when he is removed from life support.
- Sunny is revealed to be female despite Solid Snake referring to her as a male in the English version of Metal Gear Solid 2. In the Japanese version of Metal Gear Solid 2, however, there was no mention of the child's gender.
- Liquid Ocelot is revealed to have been the person who helped Naomi escape from prison. It was previously implied by Nastasha Romanenko in her novel that Solid Snake was the person responsible for Naomi's escape. Solid Snake briefly alludes to this prior account in-game in Act 2, where he mentioned that his rap sheet was modified to include his "role" in her escape as a result.
- 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.
- Solid Snake's advanced aging is revealed to have been written into his genes in order to provide a fail-safe against Big Boss' clones falling into enemy hands, or if the clones turned against the Patriots under their own volition. It was previously claimed by Liquid Ocelot that the advanced aging was the result of the clones being created when Big Boss was in his late fifties.
- Liquid Ocelot's possession by the spirit of Liquid Snake is revealed to be a result of nanomachines and hypnotherapy, rather than supernatural means.
- Though not in the game itself, the supplemental Metal Gear Solid 4 Database inferred that Ocelot's affiliation with the OMON, the Russian Tax Police's elite SWAT team and the SVR, 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.
- The Metal Gear Solid 4 Database also states that the nuclear explosion seen by Solid Snake at the end of Metal Gear was not caused by the Outer Heaven self-destruct sequence initiated by Big Boss, but by the NATO bombing run previously alluded to by Kyle Schninder in Metal Gear 2.
Metal Gear Solid: Peace Walker
- McDonell 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.
- Miller was aware of the Les Enfants Terribles project, more specifically the existence of two "sons" of Big Boss. It was previously stated in Metal Gear Solid that the only ones aware that Big Boss was Solid Snake's father during the Zanzibar Land Disturbance, were Snake himself and Roy Campbell.
- The Secret Call tape reveals that the idea behind the Patriots' AI system was first conceived in the 1970s.
- 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 mentioned by Liquid Ocelot in Metal Gear Solid 2.
- The Boss's participation in the Bay of Pigs Invasion was disinformation, as she had actually been in a coma during that time from an accident relating to the Mercury Project.
- The MSX2 user's manual of Metal Gear described Big Boss as being a former member of the Green Berets, SAS and GSG 9. Subsequent games revealed that Big Boss only served in the Green Berets and FOX before becoming a mercenary.
Metal Gear Solid V: The Phantom Pain
- In Metal Gear 2, Gray Fox reveals to Solid Snake that Big Boss had rescued him from a forced labor camp after the Vietnam War. However, this is rendered impossible due to Big Boss being in a coma over a month before the end of the war and not waking up until sometime in early 1984.
- Yevgeny Borisovitch Volgin is revealed to have survived Operation Snake Eater and fell into a coma. Earlier sources such as Portable Ops and the Metal Gear Solid 4 Database claimed he had actually been killed, with Metal Gear Solid 3 strongly implying such was the case. He eventually dies for good in Afghanistan after confronting Venom Snake.
- Kazuhira Miller loses his right arm and left leg while in Afghanistan. He was previously depicted with a full set of limbs in official artwork produced for Metal Gear Solid.
- Cipher is revealed to be the original name of the Patriots. Instead, the latter name was given to the AI network overseen by Donald Anderson.
- It is Big Boss's phantom, Venom Snake, who is killed in Outer Heaven by Solid Snake, in the original Metal Gear. While the phantom dies following the encounter, it was previously stated that Big Boss himself had fought Snake and survived the fortress's destruction.
- Ocelot mentioned that Zero founded the Patriots with Volgin's half of the Legacy. In Portable Ops, Ocelot already had the KGB's half of the Legacy when he killed the DCI to take the other half.
- The war between Big Boss and Zero is given a different context. Specifically, Zero was in a persistent vegetative state by 1984, and he initiated development of an AI system as early as 1977 in order to implement his will. A large part of the conflict between Big Boss and Cipher was because of Skull Face's actions, not Zero's. In Metal Gear Solid 4, it was implied that the Patriots' AIs started development following Big Boss's coups d'état in the 1990s, and that Zero's mental state had deteriorated simply due to sickness and old age. In addition, Big Boss told Old Snake that Zero planted the FOXDIE virus in him in order to kill the anti-Patriot faction.