In the heat of the battle, a Tz'y'gorn ship was destroyed. Not by the Ambassador. Not by any of the once-union ships.
Nightwing #3 captain: We can't lose this ship!
They were talking about the crippled shokan ship which was vulnerable to attack if all didn't go well.
Reinforcements from the Icanni and Makosami initially came because of the unofficial and accidental declaration of war,but they saw a ship. Larger than the Ambassador.