King Henry IV of England ruled from 1399 to 1413. He was the first monarch of the House of Lancaster and came to power after deposing King Richard II. His reign was marked by internal strife, including conflicts with rebellious nobles and the Welsh leader Owain Glyndŵr. Henry IV faced challenges to his authority, leading to several battles, including the notable Battle of Shrewsbury in 1403. He worked to stabilize the kingdom and strengthen the monarchy, leaving a legacy that influenced his son, Henry V, who would later achieve great military success.