The city of Antwerp and its port was captured by British 2nd Army in early September 1944. While 21st Army Group's priority at the time was Operation Market-Garden, no sense of urgency was placed in securing the approaches to the port facilities there. Walcheren Island, at the western end of the Beveland Peninsula, overlooked the Scheldt Estuary, and was strongly garrisoned by the German 15th Army who had emplaced strong concrete fortifications and large calibre guns which made it impossible to transit the waterway into Antwerp. Because of this delay, the remnants of the 15th Army "had been given the time to escape and reinforce the island of Walcheren and the South Beveland Peninsula".
The First Canadian Army was tasked by 21st Army Group to open the Antwerp area; but in the meantime had also been detailed by Montgomery to capture the channel ports of Boulogne, Dunkirk and Calais, in order to ease the logistical concerns associated with drawing supplies from the Normandy beaches. German tenacity in the channel ports meant that the Allied supply lines would continue to extend the further away the front line advanced. The channel ports were eventually "masked" when the Canadian army failed to take the ports, and attention turned to the Battle of the Scheldt. The First Canadian Army advanced north-west from the bridgehead in Antwerp and, after heavy fighting in early and mid-October, broke out onto the narrow isthmus which connected South-Beveland to the mainland.
On 9 October 1944 Field Marshal Montgomery issued a directive directing the Canadian Army to give absolute priority to the clearing of the Scheldt over any other offensive operations. and ten days later the Canadians began their approach to Walcheren Island along the isthmus. To the south of the Scheldt, the Germans had been cornered in Zeebrugge, surrendering the Breskens Pocket on November 2. Both South and North-Beveland had been virtually cleared and the time was right for the assault of Walcheren itself. For the Allies, failure to take Middelburg after the Battle of Walcheren Causeway was a disappointing prelude to Operation Infatuate.
A three-pronged assault was planned with British Commandos and part of the 52nd (Lowland) Division landing at Westkapelle in the west of the island and at Flushing in the south. The 2nd Canadian Infantry Division was to cross by a water channel close to the causeway in the east. However, in the Battle of Walcheren Causeway, it soon became clear that the tidal flats around the water channel were virtually impassable leaving the Canadians with the hazardous option of a direct assault along the well-defended causeway — an exposed stretch 40 yards wide and 1500 yards long. The Canadians established a bridgehead on the island through which the British 52nd Lowland Division attempted to pass. Against much scepticism and opposition, the plan of Lieut.-Gen. Guy Simonds (acting commander of First Canadian Army) to breach the island's dykes, and flood the interior, was adopted.
The plan to flood the island by bombing breaches in the dykes at Westkapelle, Flushing, and Veere, was controversial from the start. General Simonds, the main protagonist, thought that it would enable the attackers to approach the German positions from both the sea and the inundated-inland sides with landing craft. But the Canadian engineer, brigadier G. Walsh, who advised upon the matter pointed out that the breach would be too shallow for landing craft to pass through. The plan was apparently not discussed with the Dutch government-in-exile. When Prime Minister Gerbrandy got wind of the plan, he immediately demanded to see Winston Churchill, but Churchill denied any knowledge of the plan. When general Dwight D. Eisenhower approved of the bombing on 1 October, he appears not to have consulted the Dutch either. The military advantages of flooding the interior of the island were questionable, as it hampered both attackers and defenders. The German defenses were concentrated on the high-lying rim of the island; apart from the land-facing front in Flushing, there were no defensible positions inside the flooded area. The civilians living on the island were warned with leaflets dropped from planes to leave the area, but they had nowhere to go.:24-26