The Flanders U-boat flotillas were Imperial German Navy formations set up to prosecute the U-boat campaign against Allied shipping in the Western Approaches (British Home Waters) during the First World War.
Commanded by Kapitänleutnant Karl Bartenbach, the force comprised nine UB- and seven UC- type U-boats, small mass-produced coastal types suited for operations in the closed waters of the Channel and the North Sea.
The boats used Zeebrugge and Ostend as exit ports; UC minelayers joined in late 1915.
[2] Throughout the campaign the Flotilla grew, though losses also remained high, as the unit bore a considerable proportion of the trade war (Handelskrieg) around the British coast.
[5] Towards the end of 1918 the base at Bruges was abandoned as the German armies on the Western Front retreated.