In 1658 the Treaty of the Pyrenees brought an end to the war between France and Spain. Part of this treaty was the aquisition of the region of Roussillon (at the east end of the Pyrenees) by France. Also given to France was the northern half of the county of Cerdanya (known as Cerdagne in French), high in the mountains. This movement of the frontier left Spanish Cerdanya unprotected, so in the 1660s the Spanish fortified the town of Puigcerdà, on the south side of the border. When war broke out again in 1672, Spanish troops were able to make damaging raids across the frontier from their new fortess. Although they succeeded in capturing Puigcerdà in the closing months of the war, the French had recognised the weakness in their frontier, so the military engineer Vauban was sent to the area in 1679.
The location he chose for the new fortress was just outside Cerdanya itself, at the head of the Aude and Tet valleys and guarding the routes to Toulouse and Perpignan. The site was on high ground, protected on one side by a steep descent down to the river Tet. The new fortress was called Mont Louis after king Louis XIV, and construction began immediately. Vauban's plan was for a fortress in three sections. At the highest point of the site there was to be a square citadel with four bastions. Below this there was an area of houses (the upper town), enclosed by three bastions, and below this another area protected by a further three bastions (the lower town).
For reasons of cost, Vauban's plans were reduced to the construction of only the citadel and the upper town. The work was carried out very quickly, beginning in 1679 with the citadel reaching a state of defence by the end of 1681. The fortifications of the town were essentially complete by the end of 1682, although work continued on the details and the barrack buildings and chapel inside the citadel. One consequence of this speedy construction was poor quality masonry in the fortification walls, which had to be repaired frequently in the early years of the 18th century.
The square citadel stands at the highest point of the fortress. It has demi-lunes on three sides, the north-eastern side being a steep drop with no need for extra protection. The west bastion is doubled with a counterguard in front, to strengthen the area that was most exposed. Inside the citadel is a courtyard surrounded by barrack buildings. An interesting feature of the buildings at the edge of the citadel and the town is their roofs, which only slope inwards, not presenting a sloping face towards the enemy. Perhaps this was designed to reduce the damage to these buildings from enemy artillery fire. The ramparts of the citadel are also protected by traverses to reduce the danger from ricochet fire, which was obviously a concern.
The citadel flanks the two longest walls of the town's fortifications, which stretch down from the citadel to meet the three bastions that form its defence. These bastions are protected by demi-lunes and a strong covered way. In the flanks of the bastions there are small gates that would have allowed the defenders a sheltered route into the ditch to access the outworks and the covered way.
Mont Louis did not attract inhabitants in the way that Vauban had hoped. It was 50 years later before the town church was built and the place could be called anything other than a military outpost. This slow growth seems to justify the decision not to build the lower town that Vauban had planned, which would have increased the size of the town by half again.
The fortress of Mont Louis successfully changed the situation in Cerdanya, giving the French a strong base to operate from. Throughout the 1680s the fortress dominated the area and the governor even entered Spanish territory and took taxes there. War broke out again in 1688 and the French took control of Cerdanya until the peace of Ryswick in 1697. However the fortress was costly and did not always have the approval of the French commanders. In 1694 Vauban himself advocated that Louis XIV should demolish Mont Louis and give up Cerdanya in exchange for peace.
Visiting Mont Louis
Mont-Louis is easily accessible by road from France, Spain and Andorra, which passes close to the town. The road into Mont-Louis itself traverses the larger demi-lune of the town's fortifications. The nearby fortresses of Villefranche-de-Conflent and Fort Lagarde are within a short drive and are also well worth a visit.
The visitor is more or less free to wander the walls of the town, which are in good condition. The bastion to the left of the entrance as you enter the town contains a rather strange 'solar oven', but other than that the fortifications are unspoiled. The citadel remains property of the French army (a commando unit is stationed here), although there are signs to direct you on a "tour de la citadelle", which is a path that follows the walls (from the outside), round from the north-eastern bastion of the citadel to the main entrance to the town.