At the height of the threat of French invasion during the Napoleonic Wars, the barracks were built in 1810 as part of General Don’s military building programme. The beach at Greve de Lecq is a sandy and big enough to provide an enemy landing site, was therefore vulnerable and it needed to be defended.

On the cliffs above the barracks, on the site of an Iron Age promontory fort, Le Câtel Fort and Battery was also constructed and housed three 32-pound guns on traversing platforms. Elsewhere in the bay was Middle Battery, Valle du Fort Battery and a Round Tower. These positions required troops to man them and the barracks were built to accommodate up to 250 men. Communications were also improved by the construction of military roads linking the main defensive positions, arsenals and barracks to ensure that men and equipment could be moved swiftly to whichever part of the Island was threatened