I picked up the game on the Steam special last week.  On my 3rd attempt at single player, after reading advice in the strategy forums and dumbing down the AI, I was well on my way to dominating the map when all of a sudden the game announced that I had won a military victory.  The AI enemy still had at least 3 planets including their home planet, so I was surprised that I had won so early.

I read though the PDF manual that is supplied with SoaSE:Rebellion, and could not find any description of when the military victory is achieved.  The other victory conditions are described.  Apparently it's not required that you take all the planets, or that you wipe out their fleet.  Does anyone know exactly what the criteria is?  Thanks.