Simon de Montfort was a 13th-century nobleman and military leader in England, known for his role in the English Civil War. Born around 1208 in France, he became the Earl of Leicester and played a significant part in the conflicts between the monarchy and the barons. His leadership during the Second Barons' War was pivotal, as he sought to limit the power of King Henry III and promote the rights of the barons. De Montfort is also recognized for his contributions to the development of the English Parliament. In 1265, he summoned a parliament that included not just nobles but also commoners, which marked a significant step towards a more representative government. His efforts laid the groundwork for the modern parliamentary system in England.