Leo Winkel and the Winkelturm

Leo Winkler was born on September 15, 1885, in Cologne. After completing his architecture studies, Winkel worked as a civil engineer for the Union Deutscher Kaiser & Bergbau, before switching to the August Thyssen AG in Duisburg in 1916.

By the early 1930s, inspired by the italian campanile architecture, Winkler began experimenting with the concept of an above ground air raid shelter, that alone through its shape and form would enhance its protective capabilities. At this point, most bunkers had been constructed underground and this fact, coupled with often unpredictable building costs and times – made above ground bunkers an interesting alternative.

But money and time were not the only advantage of an above ground bunker. The impact of an exploding bomb that would dig itself into the earth was significantly less for an above ground bunker than for its underground counterpart. What this meant was that an above ground bunker could resists the pressure wave with far thinner walls.

Leo Winkel registered his first patent on the 18th of September, 1934. His design featured a standalone pointed-cylindrical air-raid shelter tower with nine floors. This approximately 20-meter-high air-raid shelter tower was intended to provide safety for 200 people. Its main feature – its tapering point, would allow bombs to slide off without causing any damage.

Winkels first design had the first two floors underground, with the remaining 7 floors above ground – as well as two entrances. One entrance was on ground level, while the second entrance was on the opposite side one a higher level. This was done on purpose to help speed up the process for people seeing shelter.

The tower was made of reinforced concrete, the staircases in the tower were intended to be made of wood and ran up vertically in the inner core of the tower. The ventilation system and air filters were located in the second underground floor.

Goats and Stukas

The Nazis decided to test the Winkel type high rise bunker (as they were officially known), and built one in Rechlin, where the military had set up a test site for new military technology. Rechlin was used extensively by the Nazis to test both new munitions as well as building techniques. The “Weißen Häuser Rechlin” was built here to test new bomb proof building structures, supposedly in an attempt to build a bomb proof new capital.

Construction of the Winkelturm was completed in early 1936 and the scientists started their tests. Goats were placed on each floor (fixed to the inner-outer wall) of the tower to test the how the pressure of an exploding bomb would affect the test subjects. Why Goats? Well goats and humans have remarkably similar hearing organs and breathing systems – making the incredibly effective and cheap test subjects.

Stukas from the affiliated Flugplatz Lärz began a series of bombing runs at the Winkelturm, dropping 500kg and 1000kg bombs, though none of them proved successful. The scientists decided then decided to attach several bombs directly on the outside of the tower and to detonate them remotely. The subsequent explosions caused all the goats to go deaf, but left them otherwise “unharmed”. The Winkelbunker survived the testing without any major damages.

This test led to the recommendation that all occupants of the bunker stay 30cm away from the inner wall to avoid going deaf when an air raid was underway. The Winkelturm can still be found in Rechlin, though when visited the site, it was completely overgrown and we had missed it.

The Winkelturm goes into mass production

Leo Winkel established his own business “L. Winkel & Co” in Duisburg at the end of 1936 and began licensing his Winkelturm to other construction companies. Initially 7 companies were granted licenses, but this was later expanded to 19.

Almost all branches of the german military began using the Winkeltürme, which had the effect that they became a state secret, and its licensing and construction plans were safely guarded. But at the end of the day, the Winkelturm was a product mean to be sold, and the L. Winkel & Co. aggressively marketed the bunker. Its small size (relative to its capacity), its affordable construction and maintenance costs as well as its customizability and “easy to find” nature made its a popular sell.

The second generation of the Winkelturm was available in four variations: Type 1, Type 2, Type 3, and Type 4 – which had space for 400, 315, 247 and 168 people respectively. The largest of the the Winkeltürme – the Type 1 – was up to 23m tall and roughly 10m wide.

When the Nazis started funding all their massive construction and armament projects, they soon ran into raw material shortages, specifically for steel, which led to Winkel being forced to reduce the amount of steel used in his bunkers as well as having him completely redesign the Winkelturm as a result. By 1938, two construction types were available, the “original” with more steel (Type 1 – 4), and the redesigned version made out of compressed concrete (Tower 1 -5).

Just like the original, the new “Turm” version came in 5 classes, offering accommodation from 164 people up to 500 people, costing between 28- and 58,000 Reichsmark. As there were so many variants of the Winkelbunker at this point, they each had their own internal naming designation, ranging from 1C, 2A, 2C, and 1D – designating each production type.

Another famous architect and bunker designer – Paul Zombeck – attempted to merge one of his patents with that of Winkel in 1938, but Winkel was having none of it and sued. Paul Zombeck lost, but that didn’t stop him from continuing to build his own air raid shelters (the majority of which can been found in Hamburg).

The Winkeltürme of Wünsdorf

We have a very long and detailed article about the Wehrmacht Headquarters in Wünsdorf (specifically the Bunker Zeppelin and Bunker Maybach) – so we are just going to give a very condensed history here.

The city of Wünsdorf, south of Berlin, has a military history dating back to 1872 – when Kaiser Wilhelm II established Prussia’s largest proving ground in the area. With the outbreak of the first world war, Wünsodrf became the headquarters of the Reichsheer. After the treaty of Versailles – the Germany military temporarily gave up the Truppenübungsplatz Zossen, but other Military installations in Wünsdorf continued to be used.

In January of 1933, the Army Command had decided that in case of an armed conflict or inner political unrest, the Stammlager Zossen should serve as the headquarters for the Oberkommando des Heeres, and that preparations for that eventually should be taken.

The Stammlager Zossen was used to establish the Kraftfahr-Lehrkomando on the 1st of November 1933, which was a secret move to build up the German Armored Troops (aka Panzertruppen). This Kraftfahr-Lehrkomando was reestablished as the Panzer-Regiment 1 in 1934. In 1935, Heereskraftfahrschule was moved into Wünsdorf, and the 3. Panzer Division was re-established in Wünsdorf. More importantly, the Nazis had decided to make Wünsdorf the headquarters of the Oberkommando des Heeres.

With the rapid military expansion in Wünsdorf, the Nazis decided to make use of the cost and time effective Winkelbunker, building a total of 19 throughout the city. The majority of the Spitzbunker were built between the large barracks, with some individual towers being placed in other strategic locations. The headquarters of the Wehrmacht only had 2 Winkeltürme as the entire complex was built underground (see Bunker Maybach – Zeppelin).

The end of the Winkelturm Production

The Nazis had underestimated their vulnerability to allied air raids, and had thus neglected to build enough air raid shelters for its larger cities. On the initiation of Albert Speer, Hitler decreed the “Führer-Sofortprogramm” on the 10th of October 1940, which sought to prioritise and speed up the construction of civilian bunkers – as well as standardising their (bunker) design.

The program was set up in three phases – the first lasting from November 1940 to November 1941, which resulted in 839 air raid bunkers for more than 400,000 people. The second phase, which lasted from 1941 to 1943 saw the creation of bomb proof shelters for an additional 500,000 people. The third phase which began in 1943, but was never completed was intended for the creation of tunnel bunkers (which would prove to be the most secure bunker type of WWII)

German construction companies had already reached their limits with the construction of the Siegfried Line and and the Atlantic Wall, and could barely deliver the materials or manpower needed for the construction of the thousands of Bunkers that were now being required.

To regain some sort of production and resource control, the Nazis tried to standardize the bunker building process, decreeing how much concrete was allowed to be used. Supposedly, this was set to roughly 3m³ per person – and any bunker which exceeded this would be banned. The Winkelturm needed substantially more concrete and was effectively banned from being built.

The Winkeltürme after 1945

Until the end of the war, over 200 Winkeltürme had been built throughout Europe – as far north as Malmö, Sweden and south as Sarajevo, Bosnia and Herzegovina. As decreed by the allied control commission, the majority of bunkers were to be torn down after 1945, though this wasn’t always as successful or easy as hoped.

Both the western allies and the Soviets decided to not always entirely follow through with this decree (often repurposing them for their own use). Of the 19 Winkeltürme in Wünsdorf, 12 were blown up while the other 7 were left standing (along with the ruins of the destroyed ones) and have since been put under monument protection.

Interestingly enough – of the 200 or so Winkeltürme that were built, there has been only 1 confirmed instance where one of the towers was destroyed during the war. On the 12th October, 1944, an american air raid over the Focke Wulf factory in Bremen scored a direct hit on a Winkelturm, causing the destruction of the tower and 5 deaths.

Of the roughly 200 towers that were built, its estimated that “only” 80 or so have survived to this day. One of the Winkeltürme in Wünsdorf has been converted into a museum, and gives a fantastic insight in not only the history of the Winkelturm itself, but also of how an air raid shelter operated during the 1930s and 40s. The other Winkeltürme in Wünsdorf have been sealed shut and the interiors are inaccessible – but can been visited from the outside.

It was originally planned to convert three of the towers into museums, but to date it seems like only one of them has been converted or is publicly. The other towers now grace the landscape of Wünsdorf, awkwardly wedged in between houses, car parks and playgrounds.

The Winkelturm Museum is part of the Garnisonsmuseum in Wünsdorf and is open from: March until October Tuesday to Friday 11:00 – 14:00Weekends / Holidays 10:00 – 17:00Tickets to the museum cost €7, while a tickets for the Winkelturm cost €1.50