The Imperium
There was at first, some semblance of a representative government, and vestiges of that would continue through the entire history of the Imperium. But political maneuvering, ever the bane of cooperative human efforts, eventually resulted in the rise of the first Imperator, Nicholas I, whose sheer force of personality and talent for outwitting his rivals gave him de facto control over the senior council and enabled him to declare himself Imperator.
Although the office of Imperator was, at least nominally, not inheritable, the Imperators tended to be very good at ensuring that their successors were loyal members of their own extended families. The result was increasingly that control of the Imperium rested in the hands of a very few Great Houses, each of whom occasionally wrested control of the Imperatorship from one of the others.
Contrary to popular belief, the Imperator was never an absolute dictator, though some were stronger than others. The Senior Council, comprised mainly of representatives of the Great Houses, always maintained some level of administrative oversight via control over the vast Imperial bureaucracy, and the Senate and Magistrates served legislative and judicial functions respectively.
But the Imperator would always be commander-in-chief of the Imperial Fleet, whose loyalty ensured that he would never lack for a big enough hammer to enforce his will.
‘Ghost’ Technology
The ubiquitous presence of augmentation technology led to one unexpected benefit. Over time it became possible to record human personalities over the course of their daily lives and later simulate that personality using a sufficiently advanced AI core. These simulated personalities inevitably became known as ‘ghosts.’
While many expressed concern that ghost technology was a violation of the restrictions on AI sentience, the usefulness of ghost advisors to the Great Houses ensured that these concerns would never really be addressed. And, since the technology to record ghosts was very expensive, only the upper classes of Imperial society had access to this form of immortality in any case. Plus, it was argued that such ghosts served as a kind of long-term cultural memory for the Imperium and thus served a valuable function in society.
The Short-Lived Victory
The Imperial structure served humanity surprisingly well in its struggle against the Collective and eventually the machines, increasingly unable to achieve a decisive victory against their creators, were forced to withdraw to the Small Magellanic Cloud rather than be hounded out of existence.
Humanity celebrated its victory against the Collective and an age of peace and prosperity ensued. But the structure which had held the Imperium together during the Machine Crusade contained the seeds of its own demise. Without an external threat it wasn’t long before the populace at large started chafing under the Imperial yoke, especially given that the centralization of control left many with limited prospects for advancement within Imperial society.