|Warning: The following information is from outside Hideo Kojima's core "Metal Gear Saga." It has some level of canonicity within the continuity, but reader discretion is advised.[?]|
Matt Campbell served in the Marines with his brother Roy Campbell. However, they eventually fell in love with the same woman. Roy Campbell, for his brother's sake, quit the Marines and decided to transfer over to the Green Berets, using the excuse that he was doing it to serve his country, which he intended to do anyway.
|Non-"Metal Gear Saga" information ends here.|
For many years, it was believed that Matt Campbell was Meryl's biological father, though it was later revealed that it was actually his brother, Roy, due to an earlier affair between the latter and Matt's wife. Matt was killed in action during the Gulf War.
Behind the scenes
Roy Campbell's brother was first mentioned in Metal Gear Solid, though his first name was only given in one of the Snake Tales chapters, featured in Metal Gear Solid 2: Substance. It is unknown whether Matt ever found out that he was not Meryl's biological father. It is possible that Meryl's mother is the same woman mentioned by Roy in Metal Gear Solid: Portable Ops.
Matt Campbell is featured in the non-canonical Snake Tales story "Confidential Legacy."
During the Cold War, Matt had been a member of a top-secret Metal Gear development project in the South American republic of Eldera to ensure the country's stability. Before that, he was working for the U.S. Part of his job was feeding falsified information to the minority separatist guerrillas. First he would pick a suitable candidate and essentially brainwash them. Matthew would then send his now-willing accomplice into the ranks of the separatists. Once there, the spy provided the Americans with useful information, selling out his comrades in the process. In his dealings with the separatists, he came to sympathize with their cause. He grew to resent the U.S. for the way it exploited smaller, weaker nations for its own gain.
In the end, Matt decided to help the guerrillas create their own nation. He wanted to give them the trump card they needed to secure their independence. Sergei Gurlukovich, who was also supporting the guerrillas, agreed to cooperate. Matt's plan was executed. The guerrillas succeeded in stealing the Metal Gear from the American base. But, when their plan was discovered, Matt was executed by the Americans. However, Snake questioned whether this account was actually true, speculating that Sergei may have lied to Meryl in order to get her to cooperate. Campbell, Matt's brother, also suspected that Sergei Gurlukovich had actually murdered Matt, to which Gurlukovich later confirmed when about to execute Snake after the latter had defeated Meryl in combat. In addition, it was also revealed that the real reason Matt accepted the mission to Eldera was because he wanted to get away from his family, as he learned the truth that his brother Roy was the true father of Meryl Campbell.