Confederate marines deployed to the base's perimeter bunkers as missile turrets fired at distant mutalisks. Recon Patrol 09 and Command Bravo confirmed that the approaching forces did not match the protoss profile and were hostile.
The initial attack waves consisted of zerglings, then zerglings with added hydralisks. The bunker line held initially and the marines inflicted heavy losses on the attackers. However the zerg could afford the casualties to wear down the defenses. Some marines were forced to fall back to the command center. The zerg continued to swarm forward and broke through to the command center, killing everybody except for Andre Madrid, who was undergoing infestation.
The zerg victory was short-lived as Executor Tassadar, Zealot Thuras and an anonymous zealot arrived and entered the command center. The anonymous zealot and the zerg present were killed. Madrid was euthanized by Tassadar. By this stage, both the terran and zerg forces had seemingly wiped each other out.
Metzen, Chris & Samuel Moore (March 29, 1999). "StarCraft: Revelations." Amazing Stories 596 (Spring): 20-27