Human Commonwealth
History
The Earth-Colonial Alliance between AEGIS and CIC form primarily as a response to the outside threats of the Zenith Imperium, the Xenocross Imperium, and the Alien Nation. Over time, as the threats seemed permanent, a more permanent political arrangement was considered, and the result would be the Human Commonwealth. The Commonwealth attempted to bridge the differences between the two factions. Earth, which had already become less powerful as its larger colonies became more populated and prosperous, lost a significant amount of its residual power and became just another world. Conversely, the Colonials were subject to a unified constitution that limited many of the abuses that had previously been tolerated under the CIC.
The end of the Xenocross threat and the rise of the Concordancy leads to the breakup of the Commonwealth, with one half (the former Earth Federacy) uniting with the Zenith Imperium to form the Imperium of Humankind, and the other half (the former Confederation) joining the Concordancy.
Society
While theoretically a united federation, in practice the Commonwealth functions as a loose association of worlds similar to the CIC. Most historians agree that the Commonwealth was in essence the CIC absorbing AEGIS, while abandoning some of the more extreme elements of the libertarian experiment.
The AEGIS Parliament and the CIC Council effectively merged and expanded to form two houses of the legislature.
Military
The battle hardened forces of the Earth-Colonial Alliance formed the new Strategic Space Forces. As a more centralized standing force than the old CIC militias, but with greater expertise in 3D warfare than the old ESF, the SSF proved to be a highly effective fighting force.