Redoute des Trois Communes, Military fortification in Saorge, France

Redoute des Trois Communes is a French fort on the highest summit of the Authion massif in Saorge, Alpes-Maritimes, at 2080 metres. Built in 1897 as part of the Séré de Rivières system, it was one of the first French forts made of reinforced concrete. Its ruined walls show pale cracked plaster with small rectangular openings, exposed stacked stone at the corner, rust-coloured streaks and a jagged broken top edge with a single rusty iron rod protruding near the corner.

Built in 1897 as part of the Séré de Rivières system, the redoubt was one of the first French forts made of reinforced concrete, raised at 2080 metres on the highest summit of the Authion massif to defend the Franco-Italian border. In World War II it was held by German troops of the 34th division. On 12 April, after artillery and aviation strikes, five volunteers of the 1st Free French Division supported by a tank obtained the surrender of the 38-strong garrison.

The fort represents a significant example of the Séré de Rivières military architecture system, showcasing how French defensive structures evolved in the late 19th century. This design demonstrates the transition from traditional to modern defensive thinking.

The redoubt is open to visitors and lies on the Chemin de Mémoire, under the authority of the Ministry of the Armed Forces. It forms part of a complex that also includes the Pointe des Trois Communes blockhouse and the Authion head barracks. At 2080 metres on the highest summit of the Authion massif, the site is exposed to sudden alpine weather, so bring clothing for cold and wind.

This fortification was among the first military structures in France built entirely from reinforced concrete, introducing modern construction methods to defensive architecture. This technical innovation was remarkable in Europe at the time of its construction and influenced future fort designs.