The Battle of Gembloux (or Battle of the Gembloux Gap) was a battle fought between French and German forces in May 1940 during the Second World War. On 10 May 1940, Nazi Germany's armed forces, the Wehrmacht, invaded Luxembourg, The Netherlands, and Belgium under the operational plan Fall Gelb (Case Yellow). The Allied Armies attempted to halt the German Army in Belgium, believing it to be the main German thrust. After the Allies had fully committed the best of the Allied Armies to Belgium on the 10th through the 12th of May, the Germans enacted the second phase of their operation, a break through, or sickle cut, through the Ardennes, and advanced to the English Channel.