With the arrival of the 21st Assault Division on Taurus IV, a broodmother on the planet rallied the zerg under her command to repel the invaders. A hive cluster with a spawning pool and roach warren was established, and reinforcements arrived via sacs. The zerg then attacked the 21st's base, overwhelming their marines and breaking their lines. The commander of the 21st was able to get out one final distress signal before falling to the zerg. The 21st Assault Division were destroyed and infested.