was supplemented by the British I Corps, 2nd Canadian Infantry Division, and II Canadian Corps, with the Polish 1st Armoured Division, British 49th and 52nd Divisions attached. Additionally the 51st (Highland) Infantry Division was to give up its transport to enable the movement of forces into battle positions. Montgomery promised the support of RAF Bomber Command in attacking the German fortifications and that of the USAAF 8th Air Force "on the day concerned". The plan for opening the Scheldt estuary involved four main operations, conducted over daunting geography: Clearing the area north of Antwerp and securing access to the South Beveland peninsula. Operation Switchback, clearing the Breskens Pocket north of the Leopold canal and south of the Western Scheldt. Operation Vitality, the capture of the South Beveland peninsula, north of the Scheldt and east of Walcheren peninsula. Operation Infatuate, the capture of Walcheren. The first attacks occurred on 13 September. After an attempt by the 4th Canadian Armoured Division to storm the Leopold Canal on its own had ended in bloody repulse, General Guy Simonds, commanding the II Canadian Corps, ordered a halt to operations in the Scheldt until the French channel ports had been taken, reporting the Scheldt would need more than one division to clear. The halt allowed the German 15th Army ample time to dig in to its new home by the banks of the Scheldt. Operation Switchback commenced on 21 September when the 4th Canadian (Armoured) Division moved north roughly along the line of the Ghent–Terneuzen Canal, given the task of clearing an area on the south shore of the Scheldt around the Dutch town of Breskens, called the "Breskens Pocket". The Polish 1st Armoured Division simultaneously pushed for the Dutch-Belgian border further east and the crucial area north of Antwerp. The Canadian 4th Armoured Division advanced from a hard-won bridgehead over the Ghent-Bruges Canal at Moerbrugge to find themselves the first Allied troops facing the formidable obstacle of the double line of the Leopold and Schipdonk Canals. An attack was mounted in the vicinity of Moerkerke, crossing the canals and establishing a bridgehead before counter-attacks forced a withdrawal with heavy casualties. The 1st Polish Armoured Division enjoyed greater success to the east as it advanced northeast from Ghent. In country unsuitable for armour, and against stiffening resistance, the division advanced to the coast by 20 September, occupying Terneuzen and clearing the south bank of the