 When his elder brother Francis, the Dauphin and Duke of Brittany, died in 1536 after a game of tennis, Henry became heir apparent to the throne.He succeeded his father on his 28th birthday and was crowned King of France on 25 July 1547 at Reims Cathedral.Henry's reign was marked by wars with Austria and the persecution of Protestants, mainly Calvinists known as Huguenots.