The Pan-Terran Imperium is an intergalactic hyperpower that encompasses tens of thousands of star systems (including tiny holdings outside of the Milky Way) and various alien races on top of it's human majority (the Ornandee, Seldik Hiveminds, and Zang'Tzk being the most notable). Although originally a military alliance of Earth's nations, it soon became a state of it's own. Considered the successor of the New Frenco Empire (who held almost all power in the organization, de facto if not always de jure), it also functions in a similar manner, being ruled in an authoritarian manner by an elite few and sporting an individualistic culture. The PTI's capital world is Earth.
Though once regarded the most powerful entity in the galaxy, a long series of various failures and setbacks in the mid-2200s allowed its chief rival, the Mechanocracy of Mankind, to eventually overtake it in power and relevance. The peak of this degradation was in 2271, where Mechanocratic fleets invaded Sol following Evgeniy Trotsky's defection to the PTI. This crippled the Imperium's military power. However, by 2300, the PTI is experiencing a rapid resurgence (attributed mostly to Joseph Hightower's return and the subsequent restructuring of the government and military buildup), and is well on it's way to return to it's previous state of unmatched strength and power.