in galactic conquest I smashed up 90+% of a fleet before mine left the battlefield (retreat button).
going back to that location the game does not show any ships on the enemy side of the map at fleet deployment, and pressing the battle button crashes the game. skipping a turn/trying again with different attack fleets have the same effect (its not a one off)
I have noticed the same thing, specifically when there are only fighters left in the opposing team forces though I don’t know if that is true of all cases. The fix is to go to (im using Windows 7)
C:\Users(profile name)\Documents\My Games\GratuitousSpaceBattles\campaignprogress(campaign name)\enemyfleets and delete the .ini files, which forces new enemy fleets to be made in that spot.