The Galactic Commonwealth was the primary body of interstellar governmental coordination from the 30th Solar Century until it, along with the rest of human civilization, collapsed sometime between the 53rd and 56th Solar Century. The Commonwealth was not so much a political organization, but a system of treaties, agreements, understandings, and threats that bound together the Human Galactic Community.
By the 29th Solar Century, the Major Colonies had long since eclipsed Earth in population and economic and political power. The Earth-Centric power structure of the Galactic Federation was no longer suitable to the task of governing 3,000 worlds spread across 11,000 light years of space. In the Solar Year 2814, Avalon colony became the first to declare that its Government was no longer subject to the rule of the Galactic Federation, after the Federation decided to recognize the independence of two of its colony worlds; Guinevere and New Albion. Avalon sent warships to reassert control over the rebellious colonies. The Galactic Federation was paralyzed with indecision and unable to respond. By mid-century, each of the Major Worlds had developed a fleet to rival that of the GF and was able to assert sovereign control over their respective sectors of space and colonial possessions. One by one, they renounced the Authority of the Central Government on Earth. The Galactic Federation contemplated war to bring the colonies into alignment but concluded it would be futile to make the attempt. The Galactic Federation continued for a time, but was a hollow shell of its former self. A depopulated and resource-depleted Earth had very little capital to expend in support of keeping the Galactic Federation afloat.
The Major Worlds recognized the value of maintaining some of the elements of the Galactic Federation. In 2887. they met at Jin Mao colony and hammered out the Initial Commonwealth Accords, which established a form for coordination among each of the Major Colonies and Earth, and established the sovereign powers of each major world:
- The power to govern their home worlds and colonies in accordance with their own laws.
- The power to build and maintain fleets of ships for galactic exploration and defense of their worlds.
- The Power to claim unexplored planets as territorial possessions.
o This last was especially offensive to Earth, which had previously held a monopoly on determining the territoriality of newly discovered worlds.
The Galactic Commonwealth collapsed around the Solar Year 5400. According to commonly accepted legend, the Commonwealth encountered a vastly superior alien species known as the Tarmigans. War with the Tarmigans obliterated all human colonies except for the small, struggling, outer colonies. When dealing with remote antiquity, it is important to remember that Real Galactic History is difficult to distinguish from stories and legends, especially since our remote ancestors produced much more of the latter than the former. Historical scholars believe that there was an interstellar governing organization prior to the Commonwealth and it was probably called the Galactic Federation. That’s about as certain as they’re willing to get, though.