Roman Catholic Answer Pope Innocent III was one of the greatest popes of the Middle Ages, please see the article at the link below for a full list of his accomplishments. There was hardly one country in Europe which was unaffected by his reign, mostly directly in one way or another. He asserted the power of the Church in Rome because King Henry VI had just died without a clear successor, leaving the throne open to a variety of people. with no clear ruler, pope innocent III could simply take control. He used the power vacuum created by the death of the king to get a grip on Rome.