The Zeebrugge Raid (French: Raid sur Zeebruges; 23 April 1918), was an attempt by the Royal Navy to block the Belgian port of Bruges-Zeebrugge. The British intended to sink obsolete ships in the canal entrance, to prevent German vessels from leaving port. The port was used by the Imperial German Navy as a base for U-boats and light shipping, which were a threat to Allied shipping, especially in the English Channel. Several attempts to close the Flanders ports by bombardment failed and Operation Hush, a plan to advance up the coast in 1917, proved abortive. As shipping losses to U-boats increased, finding a way to close the ports became urgent and a raid was considered.