It was not an easy feat for Evandrus to overcome their two powerful neighbors. A lot of their people's blood was spilled. Evandrus even suffered a plague after the war due to the rotten bodies of dead people scattered everywhere. It wasn't a pleasant memory.
Only when troops from all around the empire were gathered and Emperor Victor joined the battle at Evandrus did they finally defeat Zagaslov and Verbosa.
As much as possible, Vincent didn't want to see his people in so much suffering ever again. His only consolation was the fact that Evandrus duchy was in the opposite direction of Valyenor.
Evandrus had also become a key figure in the empire. If it was Zagaslov or Verbosa, they would have targeted Vincent's children first as an act of revenge or to stir up trouble. They wouldn't target Valyenor which was so far away.