King Henry III was the King of England from 1216 to 1272. He ascended to the throne at just nine years old after the death of his father, King John. His reign was marked by a struggle for power between the monarchy and the barons, leading to the First Barons' War. Henry III is known for his efforts to strengthen the monarchy and improve the governance of England. He commissioned the rebuilding of Westminster Abbey, which became a significant symbol of English heritage. His reign also saw the development of the English Parliament, laying the groundwork for modern democracy.