'The Admiralty M-N Scheme' was a World War I British plan to close the Strait of Dover in the English Channel to German U-boats, by means of a chain of either eight or twelve massive towers linked by
British poster made during the 1917 U-boat crisis
U-boats are naval submarines operated by Germany, especially during World War I and World War II. The term is an anglicized form of the German word U-Boot, a shortening of Unterseeboot. Austro-Hungari
U-995, a typical VIIC/41 U-boat on display at the Laboe Naval Memorial near Kiel, Germany
The first German submarine, the SM U-1. Her remains are on display at the Deutsches Museum in Munich.
The German submarine U-11, showing the kerosene vapour trail.
Sea mines are loaded in a UC coastal submarine in the harbour of Zeebrugge