Submarine pen
Bunker housing U-boats
Submarine pen
A submarine pen (U-Boot-Bunker in German) is a type of submarine base that acts as a bunker to protect submarines from air attack. The term is generally applied to submarine bases constructed during World War II, particularly in Germany and its occupied countries, which were also known as U-boat pens (after the phrase "U-boat" to refer to German submarines).
Read on Wikipedia · Image No 5 Army Film & Photographic Unit, Tanner (Lt), Public domain
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