The Fort de Dailly is the largest component of Fortress Saint-Maurice, which is in turn one of the three principal fortified regions of the National Redoubt of Switzerland.

Following an incident in which three ammunition magazines exploded in close succession in 1946, the fort was repaired and upgraded with two fully automatic 150 mm gun turrets with a range of 24 kilometres (15 mi).

After reassessments by the Swiss Armed Forces of their requirements for fixed fortifications, Dailly was progressively closed down starting in 1995, with full closure at the end of 2003.

The Fort de Dailly is the largest part of a fortress complex extending the length of the Saint-Maurice valley, with coordinated fields of artillery fire and interlocking defenses.

The Fort de Savatan adjoins Dailly at a lower level, facing to the north, and is connected by an inclined funicular in the mountain.

[6] The artillery fort is located on the end of the Dailly massif at a higher level than Savatan, with fields of fire to the north, west and south.

The fort therefore is capable of firing on an enemy advancing southeast into the heart of the Alpine redoubt from the direction of Lac Léman, or northwest from the Great Saint Bernard or Simplon passes.

It became clear that a position in the higher Dailly massif to the south would protect forces on the Savatan plateau and would complement a battery on the opposite side of the valley at Scex.

[12] Initial work installed two 150 mm mortars on Dailly at an altitude of about 3,000 metres (9,800 ft), which remained in place until the 1920s.

[14] As construction continued, rotating guns were installed to exploit the broad field of fire afforded by the heights.

Two more guns installed in an open position between Righi and the Aiguille in 1909 formed the Batterie Golèze, covering the area of Demècre.

The exposed nature of this battery led to its replacement with a rock-protected position in the 1940s, remaining in service until all 75 mm guns were withdrawn in the 1980s.

At the Battery Rossignol, elevation 1,400 metres (4,600 ft), a gallery was excavated of sufficient size to allow towed artillery to be moved, with branching galleries on either side mounting Bofors 105 mm guns with a range of 18,000 metres (59,000 ft) in ten armored positions.

[14] Dailly was the scene of an ammunition explosion on 28 May 1946, when about 5500 105 mm shells, amounting to 449 tons, exploded in three separate magazines successively.

[16] The range of these new guns approached 24 kilometres (15 mi), sufficient to reach Montreux, Sion or the Chamonix valley in France.

[17] Additional measures included the replacement of the summit batteries with two 81 mm fortress mortars, entirely buried in the mountain's peak.