Yeah, it's a major plot twist and game changer.
The army conquers all sectors of importance back with very strong troops. What will you do now?
- You can try to resist with your mercs and militia, but it won't work everywhere, and you will have many casualties.
- You can step back in the wild, regroup, and strike back. It will be hard, but maybe you can reconquer what's lost.
- Or you can move on, conquer further east, occupied by less powerful legion, get a port for reinforcements, a mine for income, gain loyalty in the nearby town, and later retaliate on the west.
- Or... You can complain, again and again, and ragequit. I don't recommend this one.