Fort de Revers
The fortifications of the town and citadel of Dunkirk had a weakness where they met the coastline. At this point there were large sand dunes on the beach. An attacking force could advance along the coast, concealed from the defences by the sand dunes, and come very close to the town. The French themselves had used this tactic against the Spanish garrison of Dunkirk in 1646 and 1658, so they were well aware of this weakness. It was originally thought that the Grand Risban would be able to provide fire coming from the sea to cover the north side of the sand dunes, but in the end it was built too far out to sea for its guns to be effective in this role. So another sea fort was built entirely for the purpose of covering the dunes and protecting the landward defences. This fort was called the Fort de Revers (the Reverse Fort) because although it was built in the sea, all its guns pointed back towards the town.
The fort took the form of a triangle, which was dictated by its function. There were two straight sides that mounted guns, facing south-east and south-west. To the south-west, the fort covered the dunes next to the citadel and to the south-east the fort covered the dunes to the north of a sector of defences known as the Tête de Nieuport, which was where the French had attacked from in 1646 and 1658. On the third side, facing towards the sea, there was a loopholed wall for musket defence, with two half-bastions.
The Fort de Revers was made of stone, like the Grand Risban, and contained accommodation and stores for the garrison. The fort is recorded as mounting 24 guns, presumably half to flank the citadel and half to flank the Tête de Nieuport. However, most plans only show 16 embrasures, so where the extra guns were placed is a mystery. Although the north-east corner of the fort was very close to the jetty, the entrance bridge actually ran parallel to the fort's east face, turning sharply to reach the gate, which was situated at the south corner. It is possible that the gate was situated here to maintain the perfect symmetry of the fort. Another possibility is that having the bridge running directly below the fort's wall offered additional protection.