History of Lorient Submarine Base in Timeline

By Popular Timelines Editorial Team · Updated: October 30, 2025

Lorient Submarine Base, constructed in Lorient, France, by the German Kriegsmarine between 1941 and 1943, served as a significant U-boat base during World War II. Following Germany's defeat, the French Navy utilized the facility until its decommissioning in 1995. Subsequently, the base transitioned into civilian use, marking the end of its military function and the start of a new chapter in its history. Its construction and operation represent a key aspect of naval warfare during the war.

June 1940: Germany Seeks French Atlantic Ports

In June 1940, after the fall of France, Konteradmiral Karl Dönitz sought to use French Atlantic ports as forward bases for the German U-boat force.

November 1940: Construction Commences on Enclosed Pens

In November 1940, construction commenced on a series of enclosed pens with bomb-proof concrete roofs on the banks of the River Scorff, adjacent to the Lorient Arsenal.

February 1941: Construction Commences on K1 Installation

In February 1941, construction commenced on the K1 installation, which included a boat lift and rails to deliver U-boats to one of 5 enclosed bays.

December 1941: Completion of K2 Installation

In December 1941, the second set of protected bays, K2, were completed opposite K1.

1941: Construction by the German Kriegsmarine

In 1941, the Lorient Submarine Base was constructed by the German Kriegsmarine.

January 1943: Allied Bombing of Lorient Begins

In January 1943, Allied aircraft began bombing Lorient to cut supply lines to the U-boat bases.

February 1943: Allied Bombing of Lorient Continues

Between January and February 1943, Allied aircraft dropped hundreds of high-explosive bombs and thousands of incendiary bombs on Lorient, flattening nearly 90% of the city.

1943: Enlargement by the German Kriegsmarine

In 1943, the Lorient Submarine Base was further enlarged by the German Kriegsmarine.

1943: Construction Begins on KIVb and KIVa

In the summer of 1943, work began on a fourth phase of construction, a set of 6 pens (designated KIVb) alongside K1 and another six (KIVa) by K2, but little more than the foundations were completed.

June 1944: Normandy Landings

Following the Normandy landings in June 1944.

August 1944: Lorient Surrounded by Allies

On August 12, 1944, Lorient was surrounded by the Allies after the breakout. The remaining U-boats were evacuated, with the last, U-853, escaping for Norway on August 27.

September 1944: Execution of Jacques Stosskopf

In September 1944, Jacques Stosskopf, a hero of the French Resistance, was executed after his activities were discovered.

May 1945: German Surrender

In May 1945, Lorient, held by the German army, was surrendered to the American Army.

1945: France (1945–Present)

The entry indicates the end of the specified event occurred in 1945.

July 1946: Renamed Base Ingénieur Général Stosskopf

In July 1946, the base was renamed by the French as Base Ingénieur Général Stosskopf, commemorating Jacques Stosskopf.

1961: Launch of Flore Submarine

In 1961, the Flore, a Daphné-class submarine, was launched and is now featured in the Keroman submarine museum.

1995: Decommissioned and Converted to Civilian Use

In 1995, the Lorient Submarine Base was decommissioned by the French Navy and converted to civilian use.

1997: Site Available for Civilian Use

After 1997, the Lorient Submarine base became available for civilian use, with the conversion of the pens into industrial units. Companies such as Plastimo moved in.