Complex sentence: He lost a battle on the bank of the Kotorosl River to Vasily II, fled to Kashin, then managed to conquer Vologda, and built up a new army with the support of Vyatka.
Split into simpler sentences: He lost a battle on the bank of the Kotorosl River to Vasily II and fled to Kashin. He then managed to conquer Vologda and built up a new army with the support of Vyatka.