Finding his conspiracies detected, he took to arms, and fortified himself in Beaugeune; but as his revolt was precipitate, before his confederates were ready to join him, he had been obliged to submit, and to receive such conditions as the French ministry were pleased to impose upon him.

Actuated, however, by his ambition, and even by his fears, he soon retired out of France, and took shelter with the duke of Brittany, who was desirous of strengthening himself against the designs of the lady of Beaujeu by the friendship and credit of the duke of Orleans.

This latter prince also, perceiving the ascendant which he soon acquired over the duke of Brittany, had engaged many of his partisans to join him at that court, and had formed the design of aggrandizing himself by a marriage with Anne, the heir of that opulent duchy.
The barons of Brittany, who saw all favor engrossed by the duke of Orleans and his train, renewed a stricter correspondence with France, and even invited the French king to make an invasion on their country.
Desirous, however, of preserving its independency, they had regulated the number of succors which France was to send them, and had stipulated that no fortified place in Brittany should remain in the possession of that monarchy; a vain precaution, where revolted subjects treat with a power so much superior! The French invaded Brittany with forces three times more numerous than those which they had promised to the barons; and advancing into the heart of the country, laid siege to Ploerrnel.

To oppose them, the duke raised a numerous but ill-disciplined army, which he put under the command of the duke of Orleans, the count of Dunois, and others of the French nobility.

The army, discontented with this choice, and jealous of their confederates, soon disbanded, and left their prince with too small a force to keep the field against his invaders.