Fort de Pré-Giroud: A Swiss Border Fortification at Vallorbe
Site at a Glance
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- Modern
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- Open
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- Modern
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- Swiss
- Site type
- Military
- Remains
- Fort
On this page13 sections
History
Fort de Pré-Giroud, also known as Fort de Vallorbe and designated A 577 by the Swiss Army, is a Swiss frontier fortification above Vallorbe in the Vaud Jura. Built between 1937 and 1939 as part of the Swiss Border Line, it was intended to block the valley toward Pontarlier and the Col de Jougne, a mountain pass crossing the Jura between the Vallorbe area and France. The fort also covered the Swiss end of the Mont d’Or railway tunnel, the Joux Valley, and the surrounding French-Swiss frontier.
Construction before the Second World War
Reconnaissance for the defense of the Mont d’Or tunnel took place in 1935 and 1936. The Bureau for Fortification Construction, reactivated in 1935, designed the installation, and work began on the steep hillside in autumn 1937. The main fort was completed during 1937 to 1939, while parts of its external defenses were added in 1941. The original construction and equipment cost four million Swiss francs.
Thirty men from Border Battalion 214 occupied the fort in August 1939 under Captain Edouard Lambelet. A detachment of the Fortress Guard Corps took over in April 1942. In 1945, Fortress Artillery Detachment 214 operated the installation with 217 men, although the limited space meant that some personnel had to live outside the fort. From 1951, responsibility passed to Fortress Company 91 and Border Brigade 1, and later to Works Company 1. The garrison fluctuated between 37 and approximately 200 personnel.
Military service and obsolescence
The first shot from one of the fort’s 7.5 cm guns was fired on 4 December 1939. Fort de Pré-Giroud and the associated Le Day defensive position formed an infantry-supported blocking system below the fort and above Vallorbe and the hamlet of Le Day. Together they protected the road and railway junction at Le Day.
The installation belonged to the prewar Swiss defensive system before strategic priority shifted toward the National Redoubt, a later plan that concentrated defense in the Alpine region. Fort de Pré-Giroud was also tactically vulnerable because its forward-facing position was exposed. Advances in weapons technology soon made it obsolete, as rockets and directly fired shaped-charge projectiles could readily target the fort. Military use ended by the middle of the 1980s, and it was decommissioned during that decade.
Preservation as a museum
The fort was sold or transferred in 1988 and came under the management of a foundation as a museum. Its preserved rooms present soldiers’ living conditions and the fort’s armament through mannequins, weapons, and documents from the Second World War. A historical display also reconstructs events at the Vallorbe border post between June 1940 and September 1944, together with the role of the infantry assigned to protect the fort. The fort and the Le Day position are recognized as a military-historical monument of national importance.
Remains
Main fort and underground layout
Fort de Pré-Giroud is excavated into a steep Jura hillside at about 1,000 metres above sea level and faces north toward the Jougne gap and the Col de Jougne. Its plan is roughly triangular, with the base at the foot of the slope. Only three freestanding structures appear above ground, while the principal spaces extend into the mountain. The underground complex contains three artillery casemates, an entrance bunker, and two infantry works linked by galleries. A double barbed-wire fence, minefields, and anti-tank obstacles surrounded the main installation.
Entrance bunker
The entrance bunker was camouflaged as a chalet and contains an entrance casemate with two machine guns. A stair shaft and freight lift descend about 30 metres to the underground level. The machine room lies directly ahead. To the left, a gas-lock leads toward the accommodation area, approximately 50 metres inside the mountain, while the route to the right reaches the five principal weapon casemates.
Living and technical spaces
The underground barracks contain a command post, office, fire-control station, telephone exchange, dining rooms, officers’ mess, kitchen, infirmary, operating room, sickroom, ammunition magazines, and sleeping quarters. Three rooms housed 27 officers and senior non-commissioned officers, while three others accommodated 103 soldiers. The kitchen served dining rooms for 60 and 40 people.
The machine room held two diesel units, an electricity generator, heating and ventilation equipment, air filtration, and a workshop. The barracks were protected by a specialized ventilation system and an air-lock chamber, features that supported continued occupation within the underground complex.
Artillery casemates
The three artillery casemates were camouflaged as rock formations. The central casemate held a semi-automatic 7.5 cm Model 1939 gun, a 4.7 cm semi-automatic anti-tank gun, and an observation post that served as the fire-control station. Each lateral casemate contained a 7.5 cm Model 1939 gun, an observation post, and a machine gun.
These artillery weapons were fortress types with narrow openings, panoramic sights, and specialized mountings. Their outer blocks were concealed by metal coverings shaped like branches, reinforcing the distinction between the rock-like artillery positions and the more domestic camouflage used for the machine-gun defenses.
Infantry defenses around the fort
Forward infantry works
Two infantry works stood forward of the artillery casemates on their flanks. One was disguised with artificial fir trees and the other as a house. Each contained a water-cooled 7.5 mm Model 1911 machine gun, an observation post, and an emergency exit. Wooden, chalet-like superstructures covered their machine-gun blocks, allowing the positions to blend with different forms of the hillside landscape.
Independent external bunkers
Three independent infantry bunkers formed the close external defense and had no underground connection to the main fort. Two stood forward and were camouflaged as houses, while the third was positioned to the rear. Each contained two 7.5 mm Model 1911 machine guns and an observation post. Built in 1941, they were identified as the eastern bunker A 579, the western bunker A 578, and the southern bunker A 5xx. Together, they carried six water-cooled 7.5 mm Model 1911 machine guns.
From 1943, these external defenses were reinforced with a 24 mm anti-tank rifle, two 8.1 cm mortars, a 4.7 cm anti-tank gun, four light 7.5 mm machine guns, and eight 9 mm submachine guns.
Le Day defensive position
The Le Day position retains ten bunkers and 15 tank barriers or other anti-tank obstacles. Its surviving and associated elements include the Grange Neuve infantry bunker A 581, GPH Le Day, the Côtette shelter, the Le Day infantry bunker, the GPH infantry bunker, the Le Day South and Le Day North infantry bunkers, the Chives à Barbet infantry bunker, the Grand Crêt infantry-gun shield, the Gaudine infantry bunker, weapons positions GPH Le Day 1 to 3, weapons positions Le Day 1 and 2, GPH Grange Neuve at Vallorbe, and the SBB bunker at Le Day.
The position also includes GPH Le Day with the artillery fort and GPH with the Le Day infantry bunker. These surviving works, together with the main fort, preserve the arrangement of artillery, infantry, and anti-tank defenses that guarded the road and railway junction at Le Day.
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