In a failed ONI operation to send Spartan-V30 back in time, the walls of reality collapsed, merging multiple timelines. A handful of Reach personnel found themselves in Boston, Massachusetts in the year 2277, two-hundred years after nuclear war had ravaged the Earth, along with survivors of the UNSC Sunrise which happened to be in slipspace at the time of the collapse. Lead by Commander Jane Desterr, the two groups banded together and built Alpha Base so they could survive in the harsh lands of the Commonwealth and figure out what is going on.