I see. Oh well, no matter since I lost. :/
A wave of over 200 Sentinel Frigates took my home planet by surprise, and when all your fleet is deployed elsewhere and defenses are still recovering from a Roaming Enclave attack, there's no chance of defeating 200 ships firing powerful shots at sniper range.
I'll probably reload an earlier save later, but this one got so difficult that I really need a break for a while.