The Battle of the Lys was a significant military engagement during World War I, taking place from April 9 to April 29, 1918. It was part of the larger Spring Offensive launched by the German Army, aimed at breaking through Allied lines in northern France. The battle involved intense fighting around the Ypres Salient, with the Allies, including British and Portuguese forces, facing heavy attacks. The battle was marked by the use of poison gas and the introduction of new tactics by the Germans. Despite initial gains, the Allies managed to hold key positions, leading to a stalemate. Ultimately, the battle highlighted the challenges faced by both sides as the war continued into its final months.