Original: Bertrand du Guesclin , or Du Gueselin ( c. 1320 13 July 1380 ) , known as the Eagle of Brittany , was a Breton knight and French military commander during the Hundred Years ' War .
Simplified: Bertrand du Guesclin ( c. 1320 -- 13 July 1380 ) , was a French knight from Brittany who fought in the Hundred Years ' War .