I have this problem, there are various races (factions) and they can move ships over systems to fight. But it gives me a headache a situation when more than 2 parties are involved.
I don't want a complex multi sides battle system, I really don't want it. The typical situation is 1 vs 1 battle and that's what will be happening most of the time. But sometimes 2 conquerors might move on the same defended planet and... yeah, what then? Who attacks whom?
Note: that battles can take more than one turn so a trick where we ressolve a battle fully after each race's move won't work.
Note 2: the game is assymetrical, 1 player and X computer opponents and their rules don't need to be the same (battle rules for computer could be different - actually in some cases these will be different for immersion purposes), so we are not limited by traditional turn order or anything like that