The main force, meanwhile, faced the front of Masséna’s army; Beresford’s detachment observed its left flank along the Tagus. But this was not all; Wellington had also taken his precautions to cast around the rear of the irregular parallelogram held by the French a screen of light troops, which effectually cut their communications with Spain, and restricted, though they could not altogether hinder, their marauding raids in search of provisions. This screen was weakest beyond Abrantes, on the line of the Zezere; but here the land was barren, and the enemy had little or nothing to gain by plundering excursions. The Castello Branco country was only guarded by its own Ordenança levy, which was trifling in force, as the whole ‘corregedoria’ from the Zezere to the Elga had only 40,000 souls, and it had sent its two militia regiments within the Lisbon lines. But, save in the small upland plain about Castello Branco itself, there was practically neither population nor tillage. The less barren and deserted mountain land between the Zezere and the Mondego was much more worth plundering, and was protected by the militia brigade of John Wilson, who lay at Espinhal on the Thomar-Coimbra road, with a force of four battalions, which ought to have numbered 3,000 men, but often shrank down to 1,500. For the militiamen, unpaid and ill-fed, deserted freely during the winter season, and as their homes lay far northward, by the Douro, it was not easy to gather them back to their colours. But Wilson had always a sufficient nucleus about him to check any marauding party that fell short of a regiment, and was a real restraint on the foragers of the 6th Corps, when they pushed out from Ourem or Thomar to gather food. He was only once seriously engaged, when, on December 23rd, General Marcognet, with two battalions and a cavalry regiment, came up against him, drove him out of Espinhal after some skirmishing, and pushed a reconnaissance as far as the Mondego, of which we shall hear in its due place. Beyond Wilson to the west, the line of observation was taken up by Trant’s militia brigade, which lay at Coimbra, to which town many of its fugitive inhabitants had by this time returned. He had a larger force than Wilson--seven militia regiments, whose strength varied from day to day but seldom fell below 3,000 men. With this irregular force he watched the line of the lower Mondego, keeping pickets out some way to the south of the river, as far as Louriçal and Redinha. They were only once driven in, when on Dec. 6th-8th one of Montbrun’s dragoon regiments pushed up the high road, and verified the fact that all the passages of the lower Mondego, including the bridge of Coimbra, were guarded.