Operation “Switchback” was conceived to capture the Breskens pcoket and liberate the south bank of the Scheldt Estuary leading to Antwerp. As the Allies moved out of Normandy in the late summer of 1944, their primary supply line remained over the invasion beaches. The logistical situation became critical as the distance fromthe beachhead lengthened. The British scored a major coup in early September when they captured the port of Antwerp. Not only was this the largest port in Europe, it had been taken with its port facilities intact. Unfortunately, there remained one problem; Antwerp lay some 50 miles from the Sea. The only approach to the port lay along the Scheldt Estuary. The Germans controlled both banks of this channel and were determined to hold out to the last. Until the land on either side could be liberated, the port of Antwerp was useless to the Allies.
Bechthold, Michael "Air Support in the Breskens Pocket: The Case of the First Canadian Army and the 84 Group Royal Air Force." Canadian Military History 3, 2 (1994)