The RTX-44 was originally developed by the Earth Federation Forces (EFF) as a next-generation main battle tank (MBT) to replace the obsolete Type 61 Tank. However, with the advent of the Principality of Zeon military's advanced mobile suit (MS), the development of the RTX-44 was integrated into the RX Project and redesigned as "a vehicle with anti-mobile suit combat capabilties." The result was a heavily-armed machine considered to be the EFF's first MS, albeit with poor mobility compared to the Type 61. Four prototypes were completed on March 20, U.C. 0078. The RTX-44 is later used as the basis for Project V's RX-75 Guntank, and in turn, the RXM-1 which would be developed into the RX-77-2 Guncannon. The remaining RTX-44 units were modified into the RTX-440 Ground Assault Type Guntank.