Lore

In 1972, the United States government initiated the covert cloning initiative Les Enfants Terribles using genetic material from the 20th century's premier warrior: Big Boss. The program yielded twin clones: Solid Snake (inheriting recessive traits) and Liquid Snake (inheriting dominant traits), alongside a third perfect clone kept in political reserve: George Sears (Solidus Snake).

Years later, Solid Snake joined the elite FOXHOUND unit. During the Outer Heaven (1995) and Zanzibar Land (1999) uprisings, Snake was forced to confront and defeat his own commanding officer and genetic father, Big Boss, as well as his former comrade Frank Jaeger (Gray Fox). Haunted by battlefield trauma, Snake retreated into Alaskan isolation as a sled-dog racer.

February 2005. During a classified military exercise on remote Shadow Moses Island in Alaska's Fox Archipelago, next-generation FOXHOUND and an army of Genome Soldiers—infantry enhanced with Big Boss's genetic therapy—launch an armed rebellion.

Led by Liquid Snake and supported by elite rogue operatives Revolver Ocelot, Psycho Mantis, Sniper Wolf, Vulcan Raven, and Decoy Octopus, they seize the facility. Holding DARPA Chief Donald Anderson and ArmsTech President Kenneth Baker hostage, they demand Big Boss's remains and one billion dollars under threat of an immediate nuclear launch.

Summoned back to duty by Colonel Roy Campbell, Solid Snake undertakes a solo infiltration mission behind enemy lines. During the operation, Snake links up with rookie operative Meryl Silverburgh and ArmsTech's chief designer, Dr. Hal Emmerich (Otacon).

As Snake progresses through the base, both Anderson and Baker suffer sudden, fatal cardiac arrests shortly after speaking with him. Snake eventually learns he was unknowingly injected by Dr. Naomi Hunter with FOXDIE, a targeted retrovirus engineered by the Pentagon to assassinate hostages and conspirators without leaving physical evidence.

Defeating the FOXHOUND commanders one by one, Snake reaches the underground gantry housing Metal Gear REX, a nuclear-equipped bipedal walker designed by Otacon that fires stealth nuclear warheads using a state-of-the-art railgun.

Tricked by Liquid Snake into activating REX using the temperature-sensitive PAL Key system, Snake engages the colossal war machine. During the battle, Frank Jaeger intervenes as the exoskeleton-clad Cyborg Ninja. In a heroic act of redemption, Gray Fox destroys REX's radome sensor before being crushed by Liquid, opening a vital vulnerability for Snake to target the cockpit.

With Metal Gear REX destroyed, Snake and Liquid battle hand-to-hand atop the wreckage as the Pentagon orders an airstrike to incinerate the facility. Following a desperate escape via jeep through the drainage tunnels, Liquid finally succumbs to the latent FOXDIE virus in the final seconds.

Snake and his surviving companion (Meryl or Otacon) depart into the Alaskan tundra on a snowmobile. Meanwhile, a secret post-credits phone call reveals Revolver Ocelot was operating as a triple agent answering directly to the President of the United States (Solidus Snake), successfully smuggling REX's combat schematics onto the global black market.