Complex sentence: Dunovant's death was one of the key factors leading to a Union victory in the engagement as it disconcerted his brigade and led to a delay in further attacks which allowed Davies to move his men to an even stronger fortified position.
Split into simpler sentences: Dunovant's death was one of the key factors leading to a Union victory in the engagement as it disconcerted his brigade and led to a delay in further attacks. This gave Davies time to move his men to an even stronger fortified position.