Created before the end of the One Year War, the YMS-18 Kämpfer Prototype was rapidly developed into different variations for specific mission roles, one of these being the heavy assault-oriented MS-18E Kämpfer. The Kämpfer Prototype featured a head-mounted commander-type antenna, large shoulder armor, and extra skirt armor which was omitted in the production model. Like its successor, numerous vernier thrusters were installed throughout the mobile suit frame, resulting in excellent speed and maneuverability.
A Kämpfer Prototype was operated by a gang of space pirates and was piloted by Akira and later, Asuna Elmarit. By U.C. 0086, the unit's parts are difficult to locate, making maintenance of the unit extremely difficult.