The Light and 4th Divisions were told off for the main attack at the three breaches. They were forced to make it on the narrow front west of the Rivillas, because the inundation cramped their approach on the right. The 4th Division, under Colville, was to keep nearest to that water, and to assail the breach in the Trinidad bastion and also the new breach in the curtain to its left. The Light Division was to devote itself to the breach in the flank of Santa Maria. Each division was to provide an advance of 500 men, with which went twelve ladders and a party carrying hay-bags to cast into the ditch. For the counterscarp not being ruined, it was clear that there would be a very deep jump into the depths. The two divisions followed in columns of brigades, each with a British brigade leading, the Portuguese in the centre, and the other British brigade in the rear. Neither division was quite complete--the 4th having to provide the guard of the trenches that night, while the Light Division detached some of its rifles, to distract the attention of the enemy in the bastions to the left, by lying down on the glacis and firing into the embrasures when their cannon should open. Hence the Light Division put only 3,000, the 4th 3,500 men into the assault. When the breaches were carried, the Light Division was to wheel to the left, the 4th to the right, and to sweep along the neighbouring bastions on each side. A reserve was to be left at the quarries below the Pardaleras height, and called up when it was needed. In addition to the main assault two subsidiary attacks were to be made--a third (as we shall see) was added at the last moment. The guards of the trenches, furnished by the 4th Division, were to try to rush the lunette of San Roque, which was in a dilapidated condition, and were to cut away the dam if successful. A much more serious matter was that, on the express petition of General Picton, he was allowed to make an attempt to take the Castle by _escalade_. This daring officer argued that all the attention of the enemy would be concentrated on the breaches, and that the Castle was in itself so strong that it was probable the governor would only leave a minimum garrison in it. He had marked spots in its front where the walls were comparatively low, owing to the way in which the rocky and grassy slope at its foot ran up and down. The escalade was to be a surprise--the division was to cross the Rivillas at a point far below the inundation, where the ruins of a mill spanned the stream, and was to drag ladders up the steep mound to the foot of the wall.