When there's more than one hostile fleet of the same faction at a system, and one of my fleets chooses the attack option in that system, the game always picks the attacked fleet for me. How is the attacked fleet determined? Is there anything I can do to affect this?
I have more than 500 hours of playtime on Endless Space.
I haven't played the game in a while, so haven't explicitly tested this, but I recall that the fleet with the highest MP is selected.
As some kind of evidence, note that you have to destroy all fleets with any MP before being allowed to attack the AI's invasion fleets, even it's just one scout ship.