49th (West Riding) Division (nicknamed The Polar Bears), who had been on the Nijmegen Island since November, came under the command of I Canadian Corps. On 2 April the division, supported by Canadian units, led Operation Destroyer to clear the Island, carefully timing the initial attack to coincide with II Corps' clearance of the east bank of the IJssel. On 3 April elements of I Corps crossed the Nederrijn east of the IJssel and met units from II Corps in the town of Westervoort opposite Arnhem. The rest of the Island was cleared within another day and the Allies occupied the southern bank of the Nederrijn in preparation for the assault on Arnhem. The original (February) plan for Operation Anger had called for an immediate crossing of the Nederrijn near Oosterbeek as soon as the river was reached, if the situation allowed it (Operation Quick Anger). Alternatively, if the German defenses were considered too strong, a better prepared crossing downstream at Renkum could be made (Operation Anger). However, Crerar had ruled that operations could not be made against Arnhem until II Corps had crossed the IJssel and advanced on Apeldoorn, and so Anger could not yet proceed. Additionally reconnaissance patrols on 3 and 4 April determined that German observation posts and positions on the Westerbouwing Heights overlooking the river would make crossing the Nederrijn dangerous. Attempts were made to create smokescreens obscuring the southern bank of the Nederrijn from the watching Germans, a technique that had proved successful in the buildup to Operation Plunder. The screen stretched from the town of Randwijk, west of Arnhem, along the south bank of the river to Huissen, south of Arnhem, but strong winds and a lack of appropriate generators reduced its effectiveness. Additionally the ground on the Island was deteriorating and on 7 April, after considering various alternatives, Foulkes decided Arnhem must be attacked from the east, across the IJssel. Preparations Allied forces The attack was necessarily delayed whilst the 49th Division moved to Westervoort and II Canadian Corps prepared to cross the IJssel further north. The move caused serious logistical problems as the roads around the Island and Westervoort became jammed with traffic. This delay caused concern that the enemy would have time to prepare for the assault, but in the event it appeared they had neither the troops or equipment to improve their situation. The attack was planned to proceed in