[2] During the Armagnac–Burgundian Civil War, in 1411, he captured the bridge of St Cloud on behalf of Charles, Duke of Orléans.
[5] Gaucourt was chosen by d'Albret and Boucicaut to help defend the town of Harfleur from the army of the English king Henry V in September 1415.
[7] When Henry's troops laid siege to the town, "de Gaucourt and his men fought back with a courage and determination that won the admiration of the English chaplain".
[11] Gaucourt was unaware of this offer until he met again with Henry,[12] but he and his fellow military commanders in the town (d'Estouteville and Guillaume de Léon) agreed to surrender.
[16] Gaucourt was later released to carry a message to the Dauphin from Henry, challenging him to one-on-one combat to end the war.
[21] After his final release "he became a major figure in the reconquest of English-held lands in France",[1] and "fought in every campaign against the English".
[22] He was described by Barker as "a medieval chivalric hero whom the modern world has forgotten",[2] and "one of the chief architects of the final expulsion of the English from France".