Following the Normandy invasion in June 1944, the Dutch civilian population was put under increasing pressure by Allied infiltration and the need for intelligence regarding the German military defensive buildup, the instability of German positions and active fighting. Portions of the country were liberated as part of the Allied Drive to the Siegfried Line. The unsuccessful Allied airborne Operation "Market Garden" liberated Eindhoven and Nijmegen, but the attempt to secure bridges and transport lines around Arnhem in mid-September failed, partly because British forces disregarded intelligence offered by the Dutch resistance about German strength and position of enemy forces and declined help with communications from the resistance. The Battle of the Scheldt, aimed at opening the Belgian port of Antwerp, liberated the south-west Netherlands the following month.