The First Ostend Raid (part of Operation ZO) was the first of two attacks by the Royal Navy on the German-held port of Ostend during the late spring of 1918 during the First World War. Ostend was attacked in conjunction with the neighbouring harbour of Zeebrugge on 23 April in order to block the vital strategic port of Bruges, situated 6 mi (5.2 nmi; 9.7 km) inland and ideally sited to conduct raiding operations on the British coastline and shipping lanes. Bruges and its satellite ports were a vital part of the German plans in their war on Allied commerce (Handelskrieg) because Bruges was close to the troopship lanes across the English Channel and allowed much quicker access to the Western Approaches for the U-boat fleet than their bases in Germany.