The Battle of Champtoceaux, often called the Battle of l'Humeau, was the opening action of the 23-year-long War of the Breton Succession. By the end of September 1341, Charles of Blois had 5,000 French soldiers, 2,000 Genoese mercenaries, and an unknown but large number of Breton soldiers in his army. Charles laid siege to the fortified castle which guarded the Loire Valley at Champtoceaux. John of Montfort could only scrape together a handful of men from Nantes to join his forces to relief the siege. Eventually John conceded defeat at Champtoceaux and rode as fast as he could for Nantes. A series of sallies by the Montfortists followed in the coming days; the French army responded and began its assaults on outlying forts held by John's forces. John was forced to surrender by the irate city council on 2 November, and he was imprisoned in the Louvre in Paris.