Complex sentence: The support of the Catawba and other "southern" tribes for the colonists led to a thirty year war of vengeance against them by the United Six Nations, one of the most brutal and overlooked conflicts in recorded history.
Split into simpler sentences: The support of the Catawba and other "southern" tribes for the colonists led to a thirty-year war of vengeance against them by the United Six Nations. This was one of the most brutal and overlooked conflicts in recorded history.