Not initially taking the threat of "mobile suits" seriously, the Earth Federation Forces are a latecomer during the One Year War when it comes to the development and production of its own mobile suits to counter the Principality of Zeon. Based on combat data from the RX-78-2 Gundam's "learning computer" system and experimental GM-type units such as the RGM-79[E] GM Precession Type, the Federation's first true mass-production unit is simply named the RGM-79 GM. The production-model GM is basically a simplified version of the original Gundam, eliminating some of the more complex and expensive features - such as the Core Block System and using normal titanium alloy armor instead of lunar titanium - to make its production faster and more economical. The GM only carries one beam saber instead of two, and has optional hand armaments of either a 100mm machine gun or a short-range - but highly effective - beam spray gun.
Though the first GM units aren't available until November UC 0079, the Federation's material and manufacturing superiority allows it to quickly catch up, fielding enough units in time to retake contested areas on Earth and to participate in the Federation's Operation Star One offensive on Zeon's space front. With the Federation Forces already on the offensive, the introduction of the GM units to the front lines assures their victory - and descendants of the GM line continue to serve the Federation Forces for at least the next fifteen years.