Kidou Senshi Gundam: Uchuu no Ixtab

During Universal Century 0079, the Magellan-class battleship Toutatis detected a Musai-class vessel heading toward Side 2 for a preemptive strike after the Duchy of Zeon declared war. The Toutatis and the Musai-class ship eventually crash-land on the Island Iffish colony, which had been devastated by poison gas. This revealed Zeon's plan to drop the colony onto Earth. The Toutatis, carrying a nuclear warhead, attempts to destroy the colony. At the same time, a Zaku platoon enters the colony by chance, having been ordered to suppress and eliminate dissent within allied forces.