Metal Gear REX

Metal Gear REX appears in the game Metal Gear Solid.

History
When REX began development, weapons company Arms Tech were in a dire state financially. With talk of a hostile takeover after the failure to obtain the contract for a new line of fighter, the chief of DARPA (then Donald Anderson) was bribed heavily to back the Metal Gear REX program and fund its development covertly. During railgun testing at a nuclear weapons disposal facility on Shadow Moses Island, REX's prototype was captured by the FOXHOUND special forces group which had been assigned to protect it. The threat of a nuclear attack was used in an attempt to extort $1 billion and Big Boss's remains from the US government.

REX's chief engineer, Hal "Otacon" Emmerich, was opposed to nuclear weaponry, and it was unlikely he would have assisted in the program if he had known REX's true purpose. He was informed that REX was intended for intercepting nuclear weapons, and REX's armaments were handled by a separate department to keep him in the dark. Their development and integration into the main chassis were out of his control, and as far as he knew, these armaments were intended to defend the REX unit itself, and to provide Theatre Missile Defense.

It became clear that REX was in fact to be used to make the nuclear strike; Otacon took it as his duty as REX's creator to destroy it. It was subsequently disabled by Solid Snake with the assistance of Grey Fox and Otacon's information.

Revolver Ocelot escaped Shadow Moses with the blueprints for REX, however, and soon sold them onto the black market. As a result, REX's epigonies spread worldwide. Snake and Otacon therefore formed Philanthropy, and sabotaged as many REX development operations as they could; the USMC's response to the REX threat was to develop a new Metal Gear, a hunter-killer to eliminate REX's descendants. It was named Metal Gear RAY.

In the game Metal Gear Solid 3: Snake Eater, the prequel to all the Metal Gear games, a Soviet scientist named Granin creates designs for a very REX-like "walking tank", and intends to them to his friend in America, who (according to Sigint) also wrote a highly-criticized paper on the topic of walking tanks.

Crew
REX is shown to be operable by one individual, as Liquid Snake is able to use it quite effectively in battle against Solid Snake and Gray Fox. It is not clear if it is intended to have additional crew. The pilot has no direct view of the world outside of the cockpit; instead information is gathered by a sensor package in a radome on the left shoulder of REX, and passed on.