October 13, 1399 - Henry Bolingbroke becomes Henry IV (the first King of the House of Lancaster) when he was crowned king of England. He had been exiled by his cousin Richard II and returned when his father, John of Gaunt, died and the King confiscated all his lands. Henry returned saying he did so just to get his father's lands back but ended up gaining enough power and support that he was crowned King. Richard was sent to Pontefract Castle and died there under "mysterious circumstances."
Henry's oldest son, Henry of Monmouth, would become the famous victor of Agincourt - Henry V.