Following the break-up of the Carolingian empire, Nominoe, Duke of Brittany, rebelled against the authority of Charles the Bald and attempted to expand into Frankish territory. When Charles placed Renaud in command of the Frankish border zone as Count of Nantes, he incurred the enmity of Lambert II of Nantes, who believed that he was the rightful heir to the County. Lambert and Nominoe intended to join forces. While Nominoe prepared an army to attack Nantes, Renaud organised the defence of the city. However, when Renaud heard that Nominoe was incapacitated due to an illness he decided to strike first against the Bretons, who were now under the command of Nominoe's son Erispoe. Frankish forces advanced from Nantes to the river Vilaine, hoping to take the Bretons by surprise. Erispoe's troop