In my book series (link here), the planets of Aurea, Ishgabangaloodoo, and most of the eastern half of the galaxy have entered an alliance against the Tatian Empire (Caput Tatiium and most of the western half of the galaxy). Weasel, the King of Aurea, is the leader of the alliance, and Tate is the leader of the Tatian Empire. However, things take a dark turn when Tate invades the planet of Awal Kabab, right on Aurea's doorstep. Confident he can defeat the smaller Tatian force, Weasel sends the entire garrison of Aurea to fight the Tatians on Awal Kabab. Although the Alliance wins a smashing but pyrrhic victory, it was a trap: Tate landed on the undefended Aurea with the bulk of their army.
Here's what needs to happen next: Now that Tate is on Aurea with an army behind him and the Alliance army is too tired and weakened from their pyrrhic victory to simply go back to Aurea and kick him out, Tate wants to take more-or-less complete control of the alliance and end the war. Here's specifically what needs to happen:
- He must take control of the Alliance Military and add it to his own
- He must successfully declare himself Emperor of the Tatian Galaxy (a new empire spanning the entire galaxy)
- He must use the new army he suddenly acquired to rapidly (as in within a few weeks) to occupy the rest of the galaxy
- Weasel and his friends must all be declared enemies of the state and forced into hiding (think order 66 from ROTS but only a few are killed)
- Tate must convince the galaxy's citizens that he is a more legitimate ruler than the old alliance
Now here's my question: Could Tate pull off a coup like this, and under what conditions would this be allowed to happen?