Prologue
The Reaper invasion of the Milky Way hit hard and fast while the galactic community was still debating if a race of sentient machines could in fact exist, although
proof of such a thing has always been known in the somewhat smaller form of the Geth. Before anyone knew what was happening the Reapers had taken Khar'shan; the Batarian home world, and spread its way across the galaxy searching for earth so they could eliminate the one race that had stopped their attempts of culling the Milky Way on multiple occasions.
Commander Shepard had been shouting at his commanding officers for months about the imminent threat that the reapers posed, ultimately it was all for nothing. During a meeting with the leaders of the Systems Alliance top brass the Reapers hit earth hard, only the Commander and his men escaped on board the SSV Normandy SR2.
Months later Commander Shepard returned with every available soul ready to make a last stand on earth. No man, woman or Reaper could have expected Shepard to return with such an army; such a thing had never been seen. The Geth and Quarian war had finally ended after three hundred years and they stood shoulder to shoulder as equals, the Turians and Salarians were joined by the krogan's, now cured of the genophage. Every race saw Commander Shepard as a beacon of hope and followed him proudly in the defence of earth. Thanks to the help of all the races involved, a super weapon was built and used in conjunction with the Citadel to stop the reapers once and for all, however the cost was steep. After the Crucible fired all Reaper based technology shut down for good, the Citadel became a floating wreck in orbit around mars and all of the mass relays that were used for near instant travel around the galaxy stopped working. Commander Shepard successfully stopped the reapers on July 18th 2187.
2206
Almost 2 decades later small cities and town started to appear across the Earth. Each of the settlements are shadows of the former selves and have erected walls to protect themselves from the local wildlife, which had changed drastically after the war. Various creatures and plant life that was on board the allied fleet have survived the descent to Earth and escaped into the wild bringing new diseases to the ecosystem. The Earths Systems Alliance was dissolved soon after the war ended and as the settlements re-established communications and safe trade routes; the Galactic System Alliance was formed with a joint council comprised of all the races and a Human at the head of the organisation.