April 17 1918, Merckem [Merkem]–Although over 90% of their country was occupied by the Germans, the Belgian Army still continued to defend their portion of the line in Flanders. Their sector had been relatively quiet since 1914, aided by deliberate flooding of much of the low-lying land in the area. Although officially not part of the Allies, the Belgians still did their best to cooperate with the forces that were helping to defend what remained of unoccupied Belgium from the Germans. When the Germans broke through south of Ypres on April 9, Belgian King Albert volunteered to extend his line south to aid the Allies.
On April 17, the Germans attacked the Belgian lines around Merckem, at the northern end of the Ypres Salient, which had been much reduced by Plumer’s withdrawal from Passchendaele. An attempted attack on the British lines the previous day had failed after the Germans realized they were attacking into nothing. Simultaneously, the Germans were attacking south of Ypres, towards Mt. Kemmel, in an attempt to take the high ground there and cut off what remained of the Ypres Salient.
The Germans had some initial success against the Belgians, but a counterattack with bayonets by the 3rd Division reversed all the German gains and captured 800 PoWs and 42 machine guns. The northern end of the Ypres Salient was secured, and the Belgians had won one of their first victories in Europe since 1914.
Sources include: Randal Gray, Chronicle of the First World War.