This type of fort was rendered obsolete following the appearance of the torpedo shell. It was decommissioned in 1889 and completely disarmed in 1912, then rearmed in emergency in 1914.
The Germans destroyed the two powder magazines and part of the northern barracks in 1918.
Created from 1936 to 1938, the fortified mole of Maulde consists of two casemates in the former fort Séré de Rivières, each equipped with two 75 mm guns, and a armor-clad observatory with two GFM type B cloches, as well as outside the fort, a third large casemate of a unique model to shelter the 155 mm GPF (Grande Puissance Filloux, or Great Power Filloux) gun, and several bunkers in the surrounding area.
The fort was involved in the Battle of the Escaut from May 20 to 26, 1940.
Here, a view from above of the A19 artillery observatory block, 20 meters high, with its two armored-clad cloches of Guetteur et Fusil-Mitrailleur (or Watcher and Rifle-Machine) type.
Be careful, if you do research on the Internet you will see that the place is dangerous and now closed to the public, following numerous accidents.
Vegetation has covered the site and may hide deep holes, not to mention the pollution linked to waste deposits of tiles and paintings from the Manufacture Française de Carrelage de Saint-Amand, which owned the premises several decades ago.

The shot was taken in may 2022, in the middle of the afternoon. Panorama made in HDR version (enfuse).

References : http://www.attila-77250.fr/Maginot/Kml/03-Escaut.kml, https://www.lignemaginot.com/ligne/sf-escaut/maulde/index.htm#10, https://inventaire.hautsdefrance.fr/dossier/pdf/d481b163-5526-4d15-a2d9-c38ec26aac91/ancien-fort-beurnonville-puis-mole-fortifie-du-fort-de-maulde.pdf?vignette=Complet, http://en.wikipedia.org/wiki/Cloche_GFM, https://wikimaginot.eu/V70_construction_detail.php?id=10458