Anarchy broke out shortly after touchdown on Oberon, resulting in looting and skirmishes between neighbors. Realizing the necessity for order, command personnel and their families banded together to form a policing force and government. This ruling class became known as the Admiralty. They assigned the colonists to duties depending on their field of expertise.
Eridani is a world of few resources. All of the colonists pulled together for many years in order to build a strong community. Some people became greedy and didn’t want to share, causing families to splinter and argue amongst themselves. A war between the families began.
The factions were at a stalemate and each began looking for ways to win. In the end, one did—sort of. They created the ultimate weapon and used it on their enemies. It was not unlike nuclear devices from the early twenty-first century.
No tests were performed, except for the small-scale, controlled detonations; they were unprepared for the full-size device. Upon detonation, a shock wave was unleashed which demolished every building and killed three quarters of the population. And it didn’t just affect their enemies, the shock wave reached the territories of all factions, even theirs.
A Mars spacecraft entered Eridani’s orbit approximately one year after the apocalypse. Upon reaching the surface, they discovered what was left of the colonists living in caves. They were maimed and malnourished. Every last surviving colonist was transported back to Mars. The injured were treated and most who were fit for duty, volunteered to fight for Earth.