The Human Covenant war has been over for ten years, in that time the UNSC has rebuilt the former civilian government, which had been disbanded during the war with the Covenant. It was a time of healing for humanity, all of the Outer-Colonies had been attacked and occupied by the Covenant, sixty planets were glassed, and the rest of the six hundred colony worlds had their settlements razed to the ground. The Inner Colonies were mostly intact, having been bypassed when the location of Earth had been discovered. Refugees had flooded into the Inner-Colonies, straining the planets individual resources. With the war over most were able to return to their original colonies to rebuild, but the worlds that had been glassed, including Reach, would take decades to Terraform back into their former selves.
A peace treaty with the Covenant Separatists was signed in 2554, stating that they would help each other in their hour of need, which the Sangheili and their allies gave in the form of humanitarian aid and helped to rebuild civilian and military infrastructure. The UNSC began to implement the reformation of a civilian government, since the military was meant to serve the people in defence of the nation, not govern it. The Unified Terran Government was formed, taking over from the old UEG. Wealth would be shared equally between the Colonies and Earth, and state rights were given as the individual colonies became self-sufficient. Corruption was thoroughly stamped out and severe punishments were given.
However through all of these changes the question that people asked the most was, what happened to the Master Chief, was he dead or was he still alive somewhere out there, trying to find his way home?