Incident: GREENBLOOD

Incident GREENBLOOD was a small, isolated event that occurred in 2582 in a planet outside charted space. The incident occurred when the small mercenary group “Death’s Head” fled from a UNSC Frigate. The group had been hired by rebel forces to assault the frigate by boarding, but had been soundly beaten by the commander, Commander James McHenry. The group, in their beat up and refitted cargo ship, fled on a random vector to escape destruction, having no time to plot a proper slipspace jump. This unfortunately resulted in a trip to a planet outside of charted space, around a small planet emitting an odd and unidentified radioactive energy. 
The mercenaries were badly damaged during the battle and slipped in inside a safe distance to the planet. Their ship was caught in the orbit of the planet, and the cargo ship, never designed for reentry, began plummeting into the atmosphere. The mercenaries escaped via escape pods to the surface, crashing with minimal supplies. Unknown to them, the UNSC craft that had repelled their attack had tracked their outgoing trajectory and transmitted it to a UNSC Destroyer, which had gone into slipspace after them in pursuit. 
When the mercenaries crashed, they were scattered. These mercenaries were under equipped, using only outdated MA4C Rifles, along with T41 Assault Armor they’d procured from the UNSC years earlier. They did however land with some small vehicles, as well as, surprisingly, an outdated and hijacked M808B/A Mobile Artillery Unit. Though the mercenaries were not aware of this, these vehicles would be crucial to their survival. While they were regrouping and finding each other, a small band of unknown aliens carefully watched their movements. 
These were the Sangheilide, a subspecies that had branched off genetically from the main species several thousand years before when they had shipwrecked and been isolated on the planet. These Sangheilide carefully watched their intruders….and formulated a plan of attack. The mercenaries did not know it, but would soon be attacked. The Sangheilide began carefully observing the survivors, and approximately two weeks after they had landed, attacked. 
The raid came in the night, without warning. The mercenaries awoke from slumber to a force of 200 Sangheilide tribesmen, armed with crude but effective plasma weapons. These weapons had been engineered from the plasma rifles, pistols, and fuel rod weapons the original survivors had crashed with. The reasons behind the attack were strictly territorial. The Sangheilide had no knowledge of the Covenant, as their ancestors had been from a Heretic sect fleeing the wrath of the Prophets, and they had no genocidal intent based on religion. Instead, they were defending their home, as they had been instructed to by the “elders”--the original survivors, who had been fearing Covenant attack and instructed their offspring to assault anyone from off planet. 
The tribesmen killed many of the mercenaries in the first few minutes of their attack, but the surviving humans regrouped and created a defensive line, and held it for several days. However, as there ammunition began running low, they faltered. The Sangheilide launched a powerful raid, killing many humans before the mercenary line reformed. Meanwhile, however, salvation was on it’s way for the mercenaries. Several days after the initial raid, the UNSC Destroyer Prodigal slipped into the system and discovered the battle raging on the surface. Uneager to aid mercenaries, but also unwilling to let fellow humans die by the hands of unknown alien aggressors, the Destroyer launched it’s small complement of infantry aboard Pelican dropships to the surface, to attempt a peace fire. 
When the dropships arrived, they were mostly successful. Though the Sangheilide used relatively highly advanced weaponry, their technological prowess was scattered, and none of the small tribes had every seen aircraft before. The gunships awed the Sangheilide fighters into ceasing their attack, and the mercenaries were rescued and brought to the destroyer. The Captain then made an executive decision and decided to return immediately to base, rather than risk personnel in a peace meeting that could potentially go wrong and get his men killed. 
When the destroyer arrived and was debriefed, ONI stepped in. They classified the incident Top Secret and swore all members of the crew to safety, while imprisoning the mercenaries. They also elected to leave the Sangheilide population alone, though a research ship was sent to observe as best as possible from low orbit.