Division predecessors they would be able to saturate the German defences which would, as a result, be unable to give supporting fire to each other's positions. Improved weather, ground conditions and supply would also be important factors. Once again, the pinching manoeuvres by the Polish and British Corps were key to the overall success. Canadian I Corps would be held in reserve ready to exploit the expected breakthrough. Once the German 10th Army had been defeated, U.S. VI Corps would break out of the Anzio beachhead to cut off the retreating Germans in the Alban Hills. The large troop movements required for this took two months to execute. They had to be carried out in small units to maintain secrecy and surprise. U.S. 36th Division was sent on amphibious assault training and road signposts and dummy radio signal traffic were created to give the impression that a seaborne landing was being planned for north of Rome. This was planned to keep German reserves held back from the Gustav Line. Movements of troops in forward areas were confined to the hours of darkness and armoured units moving from the Adriatic front left behind dummy tanks and vehicles so the vacated areas appeared unchanged to enemy aerial reconnaissance. The deception was successful. As late as the second day of the final Cassino battle, Kesselring estimated the Allies had six divisions facing his four on the Cassino front. In fact, there were thirteen. Battle The first assault (11–12 May) on Cassino opened at 23:00 with a massive artillery bombardment with 1,060 guns on the Eighth Army front and 600 guns on the Fifth Army front, manned by British, Americans, Poles, New Zealanders, South Africans and French. Within an hour and a half the attack was in motion in all four sectors. By daylight the U.S. II Corps had made little progress, but their Fifth Army colleagues, the French Expeditionary Corps, had achieved their objectives and were fanning out in the Aurunci Mountains toward the Eighth Army to their right, rolling up the German positions between the two armies. On the Eighth Army front, British XIII Corps had made two strongly opposed crossings of the Garigliano (by British 4th Infantry Division and 8th Indian Division). Crucially, the engineers of Dudley Russell's 8th Indian Division had by the morning succeeded in bridging the river enabling the armour of 1st Canadian Armoured Brigade to cross and