Sergeant Reuben Green was a member of the United States Colonial Marine Corps. He was in command of the battalion stationed at Charon Base, there to provide security for the research facility and its staff. Green was one of the few Marines deployed to Charon still alive at the time a devastating Xenomorph outbreak was unleashed upon the facility, and he subsequently battled to evacuate as many civilians as possible from the complex.
Green was one of the few survivors of the incident, escaping Charon Base aboard the Caliban.
Assignment at Charon Base
Following the construction of Charon Base, Green was placed in command of the platoon of Colonial Marines stationed at the facility. Such was the perceived importance of Professor Kleist's research, Green was placed under Kleist's command and reported directly to him.
While the Marines were officially present to provide security for the resident scientists and civilians, in reality Green's men were soon outnumbered by Larson's private security force and more often ran dangerous Xenomorph retrieval missions into the Hive adjacent to the research base, collecting live test subjects for Kleist. These dangerous assignments led to frequent casualties, and some two years after the base had started operations Green's platoon had been reduced by half from 40 men to just 20. Although faithful to the military chain of command, Green was becoming increasingly infuriated with how his men were being used by Kleist.