Founded by the Terran rebellion which sprang up against the Klingon-Cardassian Alliance in the 2370s, the IUP toppled the Alliance by 2385, "reclaiming" the Terran Empire's heritage as the dominant power in the known galaxy. (Star Trek: New Empire)
No one is certain exactly how or when events led to the IUP's founding. The date of its beginning was never revealed, although it had to occur no earlier than 2375, when the Terran rebellion was still fighting the Alliance. Sometime shortly thereafter, or perhaps as early as 2371, the rebels declared their independence from the Alliance.
- This may have happened in fact, as the rebels who had freed themselves were no longer under Alliance control; or it may have been a retroactive declaration--an interpretation of the victors rewriting history.
What is known is key factors which established it as a political power in the years immediately afterwards. Among these was the acquisition of quantum slipstream drive from the Federation, in the form of technical schematics for Quantum-class starships (such as the ISS Arcadia). QSD instantly made the former rebels a power to be reckoned with, and through the gained tactical advantage, enabled a blitzkrieg drive to victory over Alliance forces.
Another key factor was the involvement of the Overlords, a mysterious group of unseen benefactors to the fledgling rebellion, recruited by Stephen April to assist them. April believed that the former slaves (himself included), widely lacking formal education, military discipline, or the firm hand of Alliance overseers to keep them in line, would run amok and threaten their new empire with power struggles and selfish interests. April also feared a repeat of "Spock's folly", the peace-minded reforms and disarmament initiated by Spock in the 23rd century which led to the Terran Empire's destruction, and believed that the Overlords would help to avoid this course. Agreeing to April's request, the Overlords usurped power and ruled the IUP from behind the scenes, in order to safeguard the "new Empire" from both itself and external threats.
With a new fleet of starships at its command (designs for which were obtained from the Federation universe), the Imperial Union swiftly expanded over the Alpha and Beta Quadrants, conquering and occupying many former worlds of the Terran Empire, while simultaneously wearing down the Alliance. In late 2385 the Alliance dissolved as a political unit.
Although ostensibly a cooperative democracy, inspired by the Federation (upon organizational aspects of which it was patterned), the IUP was in reality a military dictatorship, where Starfleet held the real power. Starfleet's power was somewhat limited, in that it depended upon Imperial Union member-planets for personnel and resources, thus preventing wanton or wide-scale destruction of any planet resisting Imperial rule. Political machinations and avarice, in the Cabinet (the main IUP governing body) and the Imperial Council of representatives from member-worlds, compensated for this, often through "sponsorship", supporting select officers in command of starships, starbases or other key facilities.
Many races and planets in the known mirror universe, once belonging to the Terran Empire and/or the Alliance (see: mirror universe cultures), joined the IUP, willingly or by coercion. Following is a list of some of the known "members".
- In Star Trek: New Empire, the concept of Earth's destruction by the Alliance was taken from the "Shatnerverse" novels. Hence, while Terrans were part of the IUP, Earth will not be on this list.
Individuals of the following races have been seen in Starfleet service on Star Trek: New Empire, usually on the ISS Arcadia. This does not automatically indicate their membership in the IUP, however. They may have been slaves or conscripts.