1154 King Stephen of Blois (grandson of William the Conqueror) died. After the death of King Henry I, Stephen took the throne, preventing Henry's daughter Matilda from ruling, and setting off a civil war.
1400 Geoffrey Chaucer died at the age of 57. He was the first poet to be buried in Westminster Abbey.
1415, in Northern France, England led by Henry V won the Battle of Agincourt over France during the Hundred Years' War. Almost 6000 Frenchmen were killed while fewer than 400 were lost by the English.