The story followed the battles of a team of pilots who fight a savage race of aliens, called "Grelons", who have invaded all planets of a star system using superior technology. They plan to colonize the planets, using their titanic war machines to eliminate all resistance. The heroes, a small combat unit, are losing badly when their leader accidentally activates one of the Robotech Defenders. She then learns of the existence of the other machines, which are scattered on the other pilots' home planets. Each of these units has a unique range of abilities and environmental specialties (e.g., Aqualo was capable of diving and sea-based activities, Ziyon's Element was cold and snow, Thoren's heat and magma, Gartan's urban combat).