When German forces took over France in mid-1940 the race began to protect their newly won territories with bunkers and batteries designed to repel any threats.
Alongside these were many sites designed to attack those threats, including V1 and V2 launch sites, each using massive amounts of concrete.
But all these sites are tiny in comparison to the massive constructions built to protect, service, and resupply the German Kriegsmarine’s U-Boat fleet – the most terrifying and effective weapons again the Allies at the time.
During the first year of the war over 1,000 Allied ships were sunk, more than half of these fell to the U-Boat menace which patrolled the Atlantic waters in search of targets.
Originally based in German ports such as Hamburg and Kiel, there was a need for U-Boats to be located closer to their main hunting grounds and so five sites were earmarked on the western French coast.
The five sites were based at exiting French ports at Brest, Lorient, Saint Nazaire, La Rochelle, and Bordeaux and they would become the largest structures built by the Nazis outside of Germany.
In July 1940 U-Boat U30 - built in Bremen and launched in August 1936 - had entered the harbour at Lorient, the first of many submarines which would operate from here over the next four years. At this point the U-Boats weren’t protected and so Fritz Todt, Hitler’s leading engineer, was tasked with building bunkers which would protect these vital assets.
Of the five sites, Lorient on the Keroman peninsula in Brittany was the first to be built and become operational. It would become the largest of them all with seven ‘cells’ built to protect up to 13 submarines at a time. The first three cells at Lorient were completed by June 30, 1941. Using a mixture of paid workers and slave labour, they took just three months to build.
Constructions at Brest and Saint Nazaire followed and by 1942 work was progressing at the sites at La Pallice near La Rochelle and the inland U-Boat bunker in Bordeaux on the River Garronne. The plan was to be able to support up to 98 U-Boats with 30 at Lorient, 20 each at Brest and Lorient, 15 at Bordeaux, and 13 at La Pallice.
The sheer scale of the sites meant they were easily spotted by Allied aircraft and frequent bombing raids took place. However, few of the raids were effective at breaking through the 7m thick, steel-reinforced roofs. These roofs were also protected by ‘Fangrost’, a layer of reinforced concrete beams set in rows with spaces in between to create blast chambers which would dissipate the energy of bombs, including the famous ‘bunker-busting’ Tallboy.
It’s this sheer strength which ensures the bunkers are still visible today.

La Pallice U-Boat bunker
La Pallice is the primary port area of La Rochelle. From September 1940, following the capture of France by German forces, this site was initially used as a secondary base for the Italian submarine fleet which were largely based at Bordeaux.
In April 1941 work began to create a U-Boat bunker and the first two pens of what would become a complex of 10 pens was completed by October 1941 with the first German U-Boat – U-82 – arriving towards the end of November 1941.
Construction continued for two years and created a 10 cell bunker over 190m wide and 165m long with a double roof – a lower layer of 3.5m thickness of steel reinforced concrete and an upper ‘Fangrost’ layer which consisted of spaced out beams which would dissipate the energy of bombs dropped onto the roof.
The La Pallice site received a lot of attention from Allied bombers including six direct hits by Tallboy bombs. While the Fangrost layer was destroyed, it did its job, and the bombs were unable to penetrate the roof and cause damage to the inside of the bunker and its occupants.
Following the Allied landings in Normandy and the push to liberate France, these sites became a place of last stands for German troops. Under orders, Lorient, Saint Nazare, and La Pallice were to be defended to the last man.
Allied forced surrounded the site in September 1944, but it was only when orders for the unconditional surrender of Germany were received on May 8, 1945, that 20,000-strong garrison at La Pallice finally stood down.
While all of the other sites’ resident U-Boats had left their bases prior to the sites being captured, the liberation of the La Pallice site also had an added bonus in that U-766 was still inside one of the pens. This battle-damaged vessel was made seaworthy over the next few years and entered service in the French Navy in 1947 as S-09 Laubie, operating until she was broken up in March 1963.
La Pallice is still used by the French Navy today as a storage facility, but parts of the site can be visited by the public. It was also used as a location for the original Das Boot film.