As the fourth phase of the battle opened, only the island of Walcheren at the mouth of the West Scheldt remained in enemy hands. The island's defences were extremely strong and the only land approach was the long narrow causeway from South Beveland. To make matters worse, the flats that surrounded this causeway were too saturated with sea water for movement on foot, but had too little water for an assault in storm boats.

The island was attacked from three directions: across the causeway from the east, across the Scheldt from the south, and by sea from the west. To hamper German defence, the island's dykes were breached by heavy Royal Air Force bombing, which flooded the central area but allowed the use of amphibious vehicles.
The 2nd Canadian Infantry Division attacked the causeway on October 31 and, after a grim struggle, established a precarious foothold. Then, in conjunction with the waterborne attacks, the 52nd British Division continued the advance. On November 6, the island's capital Middelburg fell, and by November 8 all resistance ended.

Meanwhile, the 4th Canadian Armoured Division had pushed eastward past Bergen-op-Zoom to St. Philipsland where it sank several German vessels in Zijpe harbour.
Thus, with the approaches to Antwerp free and the area up to the Maas River cleared, the fourth phase of the Battle of the Scheldt was complete. Victory had been achieved. The Scheldt was then laboriously cleared of mines, and on November 28, the first convoy entered the port of Antwerp, led by the Canadian-built freighter Fort Cataraqui.