John III, Duke of Brittany, was present with his liege lord, Phillip of Valois, in the last war with England, on the border of the low country.

When the English retired from before Tournay Phillip dismissed his nobles.

The Duke of Burgundy was taken ill, and died at Caen, in Normandy, on the 30th of April, 1341.

Arthur II, his father, had been twice married.

By his first wife he had three sons, John, Guy, and Peter.