Aaaah, the Aurelian Federation, the pinnacle of human society. Envied by the rest of the galaxy. Life expectancy exceed 120, criminality vanish from the core systems and things like war and famine are now souvenirs or a distant past. It is true, trust me, it is not some propaganda made by the federation, everything is really fine. In fact everything is actually so fine half of the solar system want them dead.
Okay let me put things back in context. The Aurelian federation (still not an empire) was just a bunch of guys tired of the tyranny of the North Star empire (the actual empire). They said «we want more autonomy» the emperor said «fuck off» they said okay. They turn back to the rest of the Galaxy, ask for help maybe they will be more successful, nobody help. The other planets saw them either as a bunch of rebels or sleeping agents ready to wreak havoc into their own system so they said no. We don't want you, we won't help you.
So they just decide to do the only logical thing when you live under an oppressive regime: get the fuck out. They start building ships, lot of ships, like a hundred of ships. Colony class ship. They board the said ship and they set sails to where the fuck the plot decide to send them. And since they have plot armor they just find that new, green, beautiful, radiant planet in the middle of nowhere. You know what, lets say the galaxy is like the space world and solar system are like space continent. They just discover a new one. especially one green and blue planet they called it Aurelia (like in Aurelian federation) Also they happen to discover on this planet and the asteroids surrounding it the Corolith (not corona).
And now we get to the problem. I won't lose time to explain what corolith is, you guys know that every space stories get a stuff like that. Incredible energy sources space rock like that power everything, it power the ships, it power weapons, it power space suits, it power cities. It is basically space oil okay. You know what I'll call it Olith, yeah so now you know what it is at first glance. Anyway Aurelia planet seems to have a shit ton of Olith, in fact so many that they can't exploit everything in their lifetime. In two decades the society thrive, they build 3 great AI (not skynet) to manage the Community (Still not an empire). with time passing they get better, and they establish contact with the primordial galaxy. Good new they were on the verge of some ''Energy Crisis'' so the community decide to help them, you know the people who basically reject them in first place. So things went great, energy crisis aborted, trade kicked off, Aurelia start establishing diplomatic relationship with the various nation of the primal galaxy. They colonize more planet in their own solar system and they keep developing themselves.
That's where things went south, some of these planets wanted ''independence'' under the cover of asking for more autonomy and since the Aurelian community weren't made of asshole (yet) they said okay every people have the right to govern themselves so go on. Then one of the Three AI made to oversee the community development create a being which sole purpose in life is to Govern Aurelia and Aurelians. So this new being become the leader of the community and his main goal was to make Aurelia Great again. He increases the taxes on Olith,he ''peacefully'' occupy one of the three autonomous planets of the system, reverse all the trade agreement with the Empire of the North Star which piss them of.
He then declare the establishment of the Aurelian Federation and its leader (Kinda emperor) Aurelius. So now an Iron wall fall under the galaxy. You are either with the Empire or ''not'' against the Aurelian Federation.
Still not an Empire.