The Belgian army’s defense of the Yser Canal in October 1914 is referred to as the Battle of Yser. The German offensive at the Canal, which ran south from the English Channel at Nieuwport in north-western Belgium, formed part of a wider battle for control of Flanders, notably at Ypres.
The German Fourth Army, operating under Duke Albrecht, began attacking Belgian forces deployed along the Canal on 18 October with a heavy bombardment all along the Belgian lines. With the aid of British warships lying off the coast the Belgians managed to repel the German advance, the latter temporarily withdrawing to Oostende, having unsuccessfully trying to torpedo the warships.
Following repeated attacks over the following four days, a German division managed to form a bridgehead at Tervaete after a small band of troops managed to quietly cross a temporary footbridge over the Canal on 22 October without having fired a shot. This success forced the Belgians to retreat to the Diksmuide-Nieuwpoort railway on 24 October. Whilst there they received reinforcements from the French 42nd division.
At Diksmuide itself, twelve miles south of Nieuwpoort, half of the 6,500 French navy troops, the Marins Fusiliers, stationed under the command of Admiral Ronarc’h, suffered casualties or losses. Since Diksmuide formed a bridgehead to the eastern side of the canal its retention was of great importance.
With Belgian resistance weakening and the King, Albert I, fearing a German breakthrough in the direction of Dunkirk and Calais, the Belgians took the drastic step of opening of the Canal locks at Nieuwpoort on 25 October. The result was a gradual flooding of the low country between the Canal and the railway. Consequently the German Fourth Army was obliged to retreat on 29 October, transferring its offensive effort to Ypres.
Diksmuide fell to the Germans on 10 November, but Nieuwpoort remained in Belgian hands throughout the war.
(Text credited to First World War.com . . . I’m still quite busy with schoolwork)