municipality, West Flanders province, western Belgium, on the Yser (IJzer) River. Established in the 12th century as a new port for Ypres (replacing Lombardsijde), it was besieged 10 times after it was first fortified in 1163. The scene of a Dutch victory over the Spanish in 1600, it was the key to the defense of the Ypres salient in World War I. Its six sluices flooded the entire area, halting the German advance and completely destroying the town, which was rebuilt after 1918. An important port for fishing and oyster culture, it is in a coastal resort region. The North Sea resort of Nieuwpoort-Bad is 2 miles (3 km) northwest. Pop. (1992 est.) mun., 9,718.