Peter I , Duke of Bourbon Peter I of Bourbon ( 1311 – 19 September 1356 , Poitiers ) was the second Duke of Bourbon , from 1342 to his death . Peter was son of Louis I of Bourbon , whom he also succeeded as Grand Chamberlain of France , and Mary of Avesnes . Duke Peter is reported to have been somewhat mentally unstable , a trait of nervous breakdowns presumably hereditary that showed clearly for example in his daughter Joan of Bourbon , the queen , and in her son , king Charles VI of France , as well as in Peter ' s only surviving son , Duke Louis II . Early career . Peter I took part in several of the early campaigns of the Hundred Years War which broke out in 1337 . In the summer of 1339 he took part in Jean de Marigny , Bishop of Beauvais ' s failed attack on Bordeaux . In autumn 1341 he took part in the John , Duke of Normandy ' s campaign in Brittany . He was present at the coronation of Pope Clement VI at Avignon 19 May 1342 . Summer 1342 he was together with the Raoul I of Brienne , Count of Eu given command of the covering force protecting France from attacks from the north while king Philip VI campaigned in Brittany . In August 1343 he and the Dauphin of Viennois were the French ambassadors at a peace conference at Avignon , but the negotiations were fruitless as the Edward III of England declined to send any but the most junior member of the embassy . Lieutenant in Languedoc . On 8 August 1345 Peter I was appointed by Philip VI as his lieutenant on the south - west march . His opponent was to be Henry , Earl of Derby ( later Earl and Duke of Lancaster ) who completed disembarking his army at Bordeaux the day after Peter I ' s appointment . Peter I arrived to take up his lieutenancy in Languedoc in September . By then the Earl of Derby had already opened his campaign , throwing the French defences into disarray with the capture of Bergerac and the destruction of the French army present there the previous month . Bourbon set up headquarters at Angoulême and begun an extensive recruitment campaign to raise a new army , command of which fell to the Duke of Normandy . However on 21 October the Earl of Derby won another crushing victory outside Auberoche over parts of this force . The Duke of Normandy abandoned his campaign once he heard the news . In early November he disbanded his army and left for the north . The Earl of Derby exploited the absence of a French commander in the field to lay siege to the important fortress - city of La Réole . Bourbon proclaimed the arrière - ban in Languedoc and the march provinces in an attempt to find troops to relieve the siege . However the results were poor as many of the potential recruits were still on their way home from the army just disbanded by John of Normandy . Attempts by John I , Count of Armagnac to raise troops from his domains in the Rouergue also produced little . Early January 1346 the garrison of La Réole marched away under truce . Winter 1346 Bourbon kept his winter quarters at the provincial capital of Agen , a city which quickly was becoming isolated as many of the lesser towns were captured or defected to the English . Spring however opened with the so far greatest French effort in the south - west . Bourbon and the Bishop of Beauvais raised a new army at Toulouse , in part financed by the Pope whose nephew had been captured by Derby the previous year , while John of Normandy brought with him a substantial number of nobles from the north including such dignitaries as the Eudes IV , Duke of Burgundy , Raoul II of Brienne , Count of Eu the Constable of France , both Marshals and the Master of Crossbowmen . In April Normandy laid siege to the town of Aiguillon which controlled the confluence between the Lot and the Garonne . There they still remained in August when John of Normandy was urgently recalled to the north to help stop Edward III who had landed in Normandy . And so the French 1346 campaign in the south ended having accomplished nothing . Diplomatic missions . In July 1347 he took part in fruitless negotiations with the English outside Calais in the days just before that city ' s capitulation . On 8 February 1354 he was together with the Guy , Cardinal of Boulogne appointed as King John II ' s commissioners to King Charles II of Navarre , empowered to offer whatever Charles wanted . The two met the King of Navarre in the castle of Mantes , accompanied by the two dowager Queens and droves of courtiers and ministers , most of who more or less openly sympathized with Charles of Navarre . The treaty concluded 22 February granted to Charles of Navarre a considerable part of Lower Normandy which he was to hold with the same rights as the Duke of Normandy . In January 1355 he was sent together with the Chancellor of France Pierre de la Forêt on a diplomatic mission to Avignon where they were to meet with an English embassy led by Henry of Lancaster and Richard FitzAlan , 10th Earl of Arundel . The purpose of the mission was to formally ratify a peace treaty based on a draft drawn up at Guînes the previous year . However since then French policy had changed , the French ambassadors had only come to reject the English demands and had nothing new to offer . Negotiations therefore quickly broke down and the conference ended having accomplished nothing except prolonging the existing truce a few more months until 24 June . May 1355 when it became apparent that open war was about to break out between the King of France and a King of Navarre allied to England the Duke of Bourbon belonged to the party fronted by the Dowager Queens who lobbied John II on Charles of Navarre ' s behalf . In the end John II gave way and on 31 May agreed to pardon Charles of Navarre . In July the Duke of Bourbon and the Chancellor met with English ambassadors to negotiate the extension of the truce . As both the French and English governments had decided to resume the war these negotiations were naturally quite empty and fruitless . Peter was killed in the Battle of Poitiers 19 September 1356 . Marriage and issue . On 25 January 1336 he married Isabella of Valois , daughter of Charles , Count of Valois and his third wife Mahaut of Châtillon . Peter and Isabella had one son and seven daughters :