On 23 April 1918, an attempt was made by the British Navy to block the Belgian port of Zeebrugge by sinking ships weighted with concrete. The port, connected to the North Sea by Bruges canal, was an important U-boat base for the Germans. At the canal entrance was the Mole, a harbour wall and quay, protected by machine guns in its battery. There were also submarine nets across the harbour entrance. The cruiser Vindictive and modified ferries, Daffodil and Iris, deposited 200 marines, intent on destroying the mole battery. A smoke screen, intended for concealment, dispersed in high winds and the British immediately came under German fire, damaging Vindictive and generating many British casualties. The attack on the battery failed but two block ships were sunk and submarine C32 blew up the viaduct, which connected Zeebrugge to the mainland. Although a British victory, Zeebrugge was once again operational after two days.
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