Were both sides truly invested in winning it, or was the last turn a bunch of stragglers and refugees trying to get away? I don't remember that particular battle. I may have gotten wounded during that. My AT character seems to have a knack for getting wounded, but never dying.
Yes, both sides were truly invested in winning it. Darka was the defender. CE and allies attacked the region 3 turns in a row. Each attack they sent in more reinforcements. Darka won the first two battles, and lost the third. Darka retreated after the third battle.
CE and allies had to attack when they did in order to prevent too large of a lopsided battle for the first fight (enemy reinforcements were eminent). So they attacked without full forces on the first fight. Both wides brought in reinforcements on the 2nd, and CE brought in the reinforcements solely on the third.