Playing High Elf, Rebels siege Star Tower and I attack them with garrison, garrisoned lord army and outside supporting lord army.
The garrison includes 2 Eagle Claw Bolt Thrower. Both lord armies have no such unit.
During the fight, rebels cavalry attack the garrison Eagle Claw Bolt Thrower and they rout off battle.
At the end of the fight, my garrisoned lord army has an Eagle Claw Bolt Thrower it did not have before, half health and replenishing. The garrison still shows the standard 2 ECBT.
I suppose the chivalrous thing to do is disband the unit I didnt earn, but that's just not who I am ; )