Complex sentence: He thus spent two years with his fellow Separatists in the Plymouth Colony, but ultimately came into conflict with them and returned to Salem, where he became pastor in May 1635, against the objection of the Boston authorities.
Split into simpler sentences: He thus spent two years with his fellow Separatists in the Plymouth Colony, but ultimately came into conflict with them and returned to Salem. There, he became pastor in May 1635, against the objection of the Boston authorities.