the Germans could destroy it as they were planning. On 4 September, Antwerp was taken by the 11th Armoured Division with its harbour 90% intact. However, the Germans had heavily fortified Walcheren peninsula at the mouth of the Western Scheldt, establishing well dug-in artillery impervious to air attack and controlling access to the river. This made it impossible for Allied minesweepers to clear the river and open the port at Antwerp. As part of the Atlantic Wall, Walcheren peninsula was described as the "strongest concentration of defences the Nazis had ever constructed. Allied preparations On 5 September, SHAEF's naval commander, Admiral Sir Bertram Ramsay advised the Commander of 21st Army Group, General Bernard Montgomery, to make the Scheldt his main priority, stating that as long as the mouth of the river was in German hands, the port of Antwerp was useless. That same day, thanks to Ultra intelligence, Montgomery became aware of Hitler's intention to hold the Scheldt at all costs. However, Montgomery was focused on preparations for the ill-fated Operation Market Garden later that month. Among the Allied senior leaders, only Admiral Ramsay saw opening Antwerp as crucial to sustaining the advance into Germany. Montgomery had an additional incentive not to prioritize Antwerp: his apparent desire for the 21st Army Group to spearhead the invasion of Germany and capture Berlin. On 9 September Montgomery wrote to Field Marshal Sir Alan Brooke (the Chief of the Imperial General Staff) that "one good Pas de Calais port" would be able to meet the logistical needs of the 21st Army Group, though not the American armies in France. Three days earlier, on 6 September, Montgomery ordered Canadian General Harry Crerar to prioritize the capture of just such a port, Boulogne-sur-Mer. Montgomery's views obliged Eisenhower to support a plan for the 21st to invade Germany, whereas the use of Antwerp would allow all of the armies to be supplied for such an invasion. Due to these factors, little was done about Antwerp during September. On 12-13 September, Montgomery ordered the First Canadian Army to clear the Scheldt after taking Boulogne, Calais (Operation Undergo), and Dunkirk (Siege); General Crerar stated that this was impossible because he did not have sufficient manpower. Montgomery refused Crerar's request to have British XII Corps under General Neil Ritchie assigned to help clear the Scheldt, because he needed XII Corps for Operation Market Garden. Had Montgomery secured the Scheldt