How do you organize in a hurry an innovative defensive system? Through trial and error… When Germany invades France in 1940, the Atlantic coast becomes a choice location to base the submarines that should suffocate Britain. Among the ports used was Lorient, in Brittany.
The base is built by the estuary, out of the city. WWI had seen submarines, but their role was more relevant during WWII. The base is configured as an array of individual hangars for each submarine, forming concrete pods whose walls and roofs had thicknesses measurable in meters, in two parallel rows, with rails in the center to move submarines towards the lock connecting the system to the sea. Like in a modern parking, with individual slots for each ship… but for the fact that a submarine is anything but “automobile” out of the water. The system was substituted on the next stage by individual “pods” for each submarine at sea level, so each ship could get in and out easily.