The rapid advance of the Allied armies in early September 1944 had created a logistics problem: the supply lines from the improvised ports in Normandy to the front had become too long. Using the port of Antwerp would solve this problem, but after the Allied liberation of this city on 3–4 September 1944, the banks of the Scheldt Estuary were still in the hands of the German army, allowing them to block shipping to Antwerp. Especially the former island of Walcheren, at the mouth of the Western Scheldt had become a bastion, bristling with long-range coastal batteries that controlled the sea approaches. In turn this made clearing the mine fields sown by the Germans in the shipping channel to Antwerp by mine sweepers impossible. Clearing Walcheren therefore became a military necessity.