Underground galleries link the salients, caponiers and counterscarps to the central portions of the fort.

[1] The Fort de Boussois came under fire in 1914 during the opening phases of World War I, during the Siege of Maubeuge.

[3] The second phase was to add two blocks with a 75mm twin gun turret each, as well as separate munitions and personnel entries well beyond the walls of the old fort.

[3] A number of small blockhouses are associated with Bersillies, as well as a casemate: The 1940 manning of the ouvrage under the command of Captain Bertain comprised 195 men and 5 officers of the 84th Fortress Infantry Regiment.

[3][10] During the Battle of France in 1940, the invading German forces approached Maubeuge from the south and east, to the rear of the defensive line.

The Germans replied with fire from 8.8cm and 15 cm guns, hitting blocks 1 and 3 at short range.

Firing continued the next day and was extended to the other ouvrages of the sector, with aerial bombardment by Stukas.