Under Louis XIII, France entered a Thirty Years' War (1618-1648) to strengthen the natural defenses of the kingdom by incorporating the eastern provinces, notably Franche-Comté, from where the king's brother - Gaston d'Orléans – kept on intriguing against the sovereign. At the end of May 1636, the artillery troops of the Prince of Condé therefore surrounded Dole. Their modern cannons and large caliber mortars destroyed the bell tower of the Notre-Dame collegiate church, built by Hugues Sambin above the platform. Used as a watchtower, it was their first target.