| Fort de Dailly | |
|---|---|
| Part of Fortress Saint-Maurice | |
| Western Switzerland | |
 The Rhône valley with the Fort de Dailly on the heights to the right | |
  Fort de Dailly | |
| Coordinates | 46°12′25″N 7°01′43″E / 46.20692°N 7.0287°E |
| Site information | |
| Controlled by | Switzerland |
| Open to the public | From April 2014 |
| Site history | |
| Built | 1892, expanded through the 1960s |
| In use | Not in use |
| Materials | Rock excavation |
| Garrison information | |
| Occupants | Brigade de Forteresse 10 |
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. Almost entirely subterranean, the Fort de Dailly was built in the Massif de Dailly to the east of Saint-Maurice beginning in 1892. With the Fort de Savatan, it comprises a fortress complex encased in rock high above the strategic Saint-Maurice valley, capable of commanding the valley from Chillon to Martigny. It is the central component of Fortress Saint-Maurice in terms of both its position and its military power. Construction began in 1892 and the fort became operational in 1894. The fort was nearly constantly upgraded with new artillery in increasingly secure positions. 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.