He would jump on his horse, gallop away, and when he reached home he would order the drawbridge hoisted, call his vassals together, and take down his sword from the wall.

His hatred would find an outlet in terrific explosions of wrath.

It was the time of frightful passions and victorious rages.

The oath?
The Pope would free him from it, and the ransom he simply ignored.
When Clisson was imprisoned in the Chateau de l'Hermine, he promised for his freedom a hundred thousand francs' worth of gold, the restitution of the towns belonging to the duke of Penthievre, and the cancelling of his daughter Marguerite's betrothal to the Duke of Penthievre.

But as soon as he was set free, he began by attacking Chateladren, Guingamp, Lamballe and St.Malo, which cities either were taken or they capitulated.