Ouvrage Janus, Maginot Line fortification in Montgenèvre, France

Ouvrage Janus is a Maginot Line artillery work built from 1931 on the ridge of Mont Janus, at 2,450 m, above Briançon. It has eight blocks: a mixed entry, infantry and artillery casemates, observation blocks and, at its centre, the old Fort Janus 95 mm naval-gun casemate. A stone perimeter wall with rounded embrasures links the ruined two-storey barracks to the concrete blocks; the 1940 Italian bombardment damage is still visible.

A Séré de Rivières fort was begun on Mont Janus in 1883, with a rock-cut battery of four 95mm naval guns added between 1898 and 1906. The Maginot ouvrage was built from 1931, halted in July 1935 after the Stresa Front agreement, and resumed in 1938. On 21 June 1940, French 280mm mortars guided by Janus observers silenced the Italian guns of Fort Chaberton.

The site takes its name from the massif, already called Château Jouan at the end of the 18th century, where a Vauban-era round tower stood. The Maginot work was dug beneath the older Fort du Janus and kept its rock-cut 95 mm naval gun casemate, so two generations of fortification share one ridge. The position is closed to access.

The Maginot positions are closed to access and the above-ground portion is unsecured, so the site can only be viewed from outside. It stands at 2,540 m near the Col de Montgenèvre, east of Briançon, reached on foot; damage from the June 1940 Italian bombardment remains unrepaired. The commune of Montgenèvre owns the site, under study for public access.

The 95mm naval guns of Block 8 came from the earlier Fort du Janus, whose rock-cut casemate was built between 1898 and 1906 and later absorbed into the Maginot work. On 21 June 1940, observers at Janus directed French 280mm mortar fire that silenced the Italian guns of Fort Chaberton.