The Sihl plain near Einsiedeln was cleared in the 1930s to make way for a reservoir. The Swiss military conducted tests with aerial bombs before the water came. Picture from a report in the Zürcher Illustrierte. — The Sihl plain near Einsiedeln was cleared in the 1930s to make way for a reservoir. The Swiss military conducted tests with aerial bombs before the water came. Picture from a report in the *Zürcher Illustrierte*. e-periodica

The bombing of the Sihl plain

The damming up of Lake Sihl to create a reservoir started on 30 April 1937. A few days later, the Swiss air force bombed two vacated farmhouses in the area designated for the lake as part of a training exercise. The media interest was huge. Hundreds of people who had been evacuated from their homes to make way for the reservoir also followed the spectacle.

Adi Kälin

Adi Kälin is a historian and freelance journalist.

Lake Sihl near Einsiedeln is Switzerland’s biggest reservoir in terms of surface area at about 11 square kilometres. That is how much land was flooded when the dam was completed in 1937: 45 per cent of the area was just peat and bogland, although 41 per cent was also pasture and meadow. Many buildings had to be vacated to make way for the lake: 93 residential buildings, 124 barns with stables, 13 field barns, 179 peat huts and 14 other buildings including sawmills, chapels and covered bridges. Only about a third of the families affected were rehoused near the lake shore.

**A view of the Sihl plain before it was flooded, dating from the early 1930s.** Klosterarchiv Einsiedeln

An earlier reservoir construction project by Maschinenfabrik Oerlikon had come to nothing. In 1909, the Swiss federal railways became involved and founded Etzelwerk AG in partnership with Nordostschweizerische Kraftwerke AG (NOK) for the construction and operation of the future power station. Three cantons and two districts issued the requisite authorisation. In Einsiedeln about 80 per cent of voters approved the project on 28 November 1926 with a two-thirds majority.

A project that fascinated the public

The damming was to start at the end of April 1937, but all the buildings had to be cleared and demolished first. The Einsiedler Anzeiger reported on 19 March 1937: “Communities are disappearing around Lake Sihl. Houses are falling like dominos. It is a sad sight to see them being torn down.” There was great interest in the new reservoir and a curious public flocked to the site. The national press could not stop reporting on it. The passenger ships on Lake Zurich teamed up with the Südostbahn railway to offer extra trips to the site: “A marvellous opportunity to visit Etzel mountain and Lake Sihl”, as a newspaper advertisement reported in the summer of 1937 in a number of Zurich newspapers. The lake reached peak storage height for the first time on 13 September.

**The damming began at the end of April 1937. The view of Willerzell from the village of Gross.** Klosterarchiv Einsiedeln

The Abbot of Einsiedeln blessed the reservoir, the site and the two new viaducts on 12 May. The head of the cantonal government in Schwyz (Landamman) August Bettschart mentioned in his speech, as he had done on a number of other occasions, that despite all the joy about the successful project, they could not forget the pain felt by many of the locals when they saw the lake blotting out the centuries-old cultivated land: “Our men and women stand on the slopes around the reservoir, silent and deeply disturbed by the lake’s growing size.” Bettschart also mentioned that there were about 50 evacuated families in Einsiedeln who didn’t know where to go.

The Einsiedeln area before the construction of the reservoir. — **The Einsiedeln area before and after the construction of the reservoir.** swisstopo / swisstopo

The Einsiedeln area after the construction of the reservoir. — **The Einsiedeln area before and after the construction of the reservoir.** swisstopo / swisstopo

The Federal Department of Defence (FDoD) meanwhile proceeded with its “interesting exercise in destruction”, as reported in an article by the Bund newspaper. Two farmhouses vacated for the reservoir had been bought to test the new planes and aerial bombs. The method for taking aim was extremely rudimentary: lines were painted on the outside of the plane, which the aircrew member would use to locate the target on the ground. At the right time he would instruct the pilot to release the high-explosive 50-kilogram bombs and the 1.5-kilogram firebombs.

Waiting for the bombardment

Airforce officers had inspected the two farmhouses weeks before the exercise. Only an approximate time was given for the bombing to avoid having too many people coming to watch. It was to be between 3 and 8 May 1937. The inhabitants of Einsiedeln and the surrounding area kept a close eye on any incoming vehicles so as not to miss the moment. On 4 May it was action stations: four black vehicles with military numbering travelled through Einsiedeln with Federal Councillor Rudolf Minger, head of the department of defence, in the leading one. The following vehicles all contained high-ranking members of the military. At the rear was a coach with about 30 recruits from Dübendorf flying school. The vehicles traversed the first viaduct, which had recently opened, to Willerzell and continued towards ‘Bruderhöfle’, the first property to be targeted by the planes. The recruits cordoned off a wide area around the farm.

**The new Willerzell viaduct, photographed in 1936.** e-pics

The first attempts involved buried bombs before dropping the high-explosive and finally firebombs. An illustrated report in weekly newspaper Zürcher Illustrierte contained a number of striking photographs demonstrating the effect of a high-explosive bomb, which fell about a metre from the building. The article said: “The detonation could be heard over 10 km away. It left an 8-metre wide and 2.5-metre deep crater. Stones, clods of earth, roof tiles, boards and other parts of the house were sent flying up to 80 metres in the air. Part of the building collapsed sideways and almost entirely disappeared into the crater.” One of the pictures is very blurred. That was due to the ground shaking from the bombs as apologetically explained in the article. The photographer was 500 metres from the house, which was how far the bomb fragments reached. One of the fragments, about eight centimetres long, is shown in the report.

Next up was the second house in the direction of the hamlet ‘Birchli’. The slopes were “full of spectators” by then according to a report in the Neue Zürcher Nachrichten (NZN). The people followed the dive and dropping of the bombs “with bated breath”. “Aerial bombardment in the Lake Sihl basin” was the headline in Der Sonntag magazine. The NZN concluded its report thus: “The people experienced a sensation and a rare, remorselessly destructive spectacle. Something we hope never to see for real.”

The Zürcher Illustrierte dedicated three full pages to the bombing on the site of the artificial Lake Sihl. — **The *Zürcher Illustriert*e dedicated three full pages to the bombing on the site of the artificial Lake Sihl.** e-periodica

A displaced family

The Zürcher Illustrierte published a picture of the Grätzer family moving out of ‘Bruderhöfle’ two days before the bombing. The Grätzers and their three children had only moved into the house, built in 1874, in 1930. The father was a forest worker in the village of Binzen and also managed a bike repair shop. Author Marlis Schuler-Kälin provided a highly detailed account of what happened to the affected houses and families in a four-volume work. It also contained a report by the Grätzers’ son about leaving ‘Bruderhöfle’: “In April 1937, we bid a tearful farewell to our old home”. The family moved a number of times after that before settling in Horgenberg where the father worked as a night watchman for business premises and hotels. The mother died in 1969 and her husband seven years later.

**The Grätzer family who had to leave the Sihl plain. The Zürcher Illustrierte also showed a located bomb splinter.** e-periodica

Just under seven years after the bombing, Einsiedeln was to receive a taste of real war. An English bomber that had been involved in the RAF’s disastrous raid on Augsburg had been so hard hit by German anti-aircraft fire that it diverted to Switzerland and exploded in a big fireball over Lake Sihl. The Einsiedler Anzeiger reported that the explosion had been so powerful that “people were thrown around in their beds while the furniture shook and entire houses vibrated.” The aircrew had managed to vacate the airplane shortly before the explosion, only one crew member who had already been injured died after his parachute jump. The frozen Lake Sihl, however, resembled a giant field of debris; only the heaviest pieces of debris penetrated the ice.

These days, Lake Sihl looks like it’s been there forever. No trace remains of the natural and cultivated landscape from the 1930s, which now lies almost 20 metres under the water.

**The Sihl reservoir...** e-pics
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**... took the place of the Sihl plain.** e-pics
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**Bridges were built and houses relocated before the lake was built...** Klosterarchiv Einsiedeln
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**... or bombed as part of a military exercise.** e-periodica
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**The area was flooded in spring 1937 ...** Klosterarchiv Einsiedeln
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**... and sank forever into the depths of Lake Sihl.** e-pics
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More of: 20th / 21st century Economy War/battle

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