On the next morning the actual siege began. It was destined to last from December 20 to February 20, and may be divided into three well-marked sections. The first comprises the operations against the Spanish outworks, and terminates with the capture of the two great bridge-heads beyond the Huerba, the forts of San José and Our Lady of the Pillar: it lasted down to January 15. The second period includes the time during which the besiegers attacked and finally broke through the main _enceinte_ of the city: it lasts from January 16 to January 27. The third section consists of the street-fighting, after the walls had been pierced, and ends with the fall of Saragossa on February 20. Having reconnoitred the whole circuit of the Spanish defences on the very evening of their arrival before the city (December 20), Moncey and Mortier recognized that their first task must be to evict the Spaniards from the Monte Torrero, the one piece of dominating ground in the whole region of operations, and the spot from which Saragossa could be most effectively attacked. They were rejoiced to see that the broad hill was not protected by any continuous line of entrenchments, but was merely crowned by a large open redoubt, and defended in front by the two small bridge-heads on the Canal of Aragon. There was nothing to prevent an attempt to storm it by main force. This was to be made on the following morning: at the same time Gazan, on the left bank of the Ebro, was ordered to assault the suburb of San Lazaro. Here the marshals had underrated the strength of the Spanish position, which lay in such low ground and was so difficult to make out, that it presented to the observer from a distance an aspect of weakness that was far from the reality.