Ouvrage Barbonnet, Military museum in Sospel, France

Ouvrage Barbonnet is the Maginot work built 1931-1935 on Mont Barbonnet above Sospel, entirely subterranean with two blocks: an entry block and an artillery block facing Italy, with galleries, usine and magazines running under the east side of the old Fort Suchet at 748 metres. The older Séré de Rivières fort crowns the peak at about 850 metres, a rough trapezoid ringed by a wall and ditch with three caponiers, its caserne vaulted and earth-covered, and two 155 mm Mougin twin turrets, Jeanne d'Arc and Bayard, each six metres across and about 180 tonnes.

The original fort was built starting in 1883, then significantly expanded between 1931 and 1935 with modern Maginot-style fortifications. This second phase of construction responded to changing threats along the French-Italian border.

The two works kept separate garrisons: Fort Suchet was manned in 1940 by elements of the 157th and 158th Régiments d'Artillerie de Position, while the Maginot ouvrage was held by the 95th Brigade Alpin de Forteresse, which also provided infantry support on the surface. Captain Imbault commanded the whole position. The Maginot kitchens fed both garrisons, but the men ate in separate mess halls.

The site sits at 850 m on Mont Barbonnet, 2 km south of Sospel, above the Nice–Col de Tende road. The Séré de Rivières fort and the Maginot ouvrage are separate structures: the Mougin battery is not linked to the subterranean Maginot galleries, whose Block 2 lies just south of the old fort's walls. Both may be visited in summer and house a museum.

The two Mougin twin turrets, "Jeanne d'Arc" and "Bayard", were made by Châtillon-Commentry in Montluçon: 6 m across, 1.5 m high and about 180 tonnes each, turned by a steam engine and not retractable. After 1945 the guns were replaced with pieces from Fort de Frouard and Fort de Villey-le-Sec; the Bayard guns went back to Villey-le-Sec in 1963, where that turret works again.