The first route of the defensive system was undertaken in 1637 by Gaspard de Champagne, Comte de la Suze and Seigneur de Belfort. The fortified pentagonal enclosure is entirely built by Marshal Vauban, at the request of Louis XIV. Aware of the strategic stakes of the position of the city, it makes a real war square and doubles its area: the western part (from the Place d'Armes to the Prefecture) is organized on a regular route, contrary to the eastern part (from the Place d'Armes to the Jules Heidet school) which remains on a less regular medieval plan.