The Battle of the Lys was a major battle between Belgian and German forces during the German invasion of Belgium of 1940 and the final major battle fought by Belgian troops before their surrender on 28 May. The battle was the bloodiest of the 18 Days' Campaign. The battle was named after the Leie, the river at which the battlefield occurred.

Moritz Albrecht Franz Friedrich Fedor von Bock was a German Generalfeldmarschall who served in the German Army during the Second World War. Bock served as the commander of Army Group North during the Invasion of Poland in 1939, commander of Army Group B during the Invasion of France in 1940, and later as the commander of Army Group Center during the attack on the Soviet Union in 1941; his final command was that of Army Group South in 1942.