Almeida and Elvas, Peniche and Abrantes, were regular fortresses with large garrisons. There were, however, other points where Wellington ordered fortifications of a less permanent kind to be thrown up, because he thought them of first-rate strategical importance. The two most important were one on the northern line of advance which the French might take, the other on the central or Castello Branco line. The first was a line of redoubts behind the river Alva, just where it joins the Mondego, on either side of the bridge and village of Ponte de Murcella. It was here, he thought, that Masséna would choose his road, along the south bank of the Mondego, if he marched on Lisbon by the Beira line. But the Marshal moved by Vizeu, partly (as it seems) because he had heard of the fortifications of this defile, and the works were never used. Equally unprofitable (so it chanced) was another important series of field-works, constructed to cover the lowest reach of the Zezere against an invader who should come by the Castello Branco road, and should have masked or taken Abrantes. This was a line of redoubts and trenches, almost a fortified camp, on the east bank of the river from Tancos to opposite Martinchel, blocking both the roads which lead from Castello Branco into Estremadura. Masséna, coming not by the route which was guarded against, but from Leiria and Thomar, took the lines of Zezere in the rear, and they proved useless. Along with the precautions taken on the banks of the Alva and the Zezere, two other pieces of engineering must be mentioned. The one, the destruction of the _Estrada Nova_,--the mountain-road which leads from Fundão and Belmonte to the lower Zezere without passing through Castello Branco,--has already been noticed, when we were dealing with the possible lines of invasion in Portugal. The other move was constructive, not destructive, in character. Foreseeing that Abrantes might be masked, or besieged on the northern bank of the Tagus, and all the roads in that direction thereby blocked, while it might still be very profitable to have free communication between Lisbon and the Castello Branco region, he caused the road above the south bank of the Tagus, from opposite Abrantes to the flying-bridge at Villa Velha, to be thoroughly reconstructed. This route, by Gavião and Niza, was so much easier in its slopes than the old high-road Abrantes-Castello Branco, that, even when the latter was safe, troops moving from east to west, along the Tagus often used it during the next two years of the war, though it involved two passages of the river instead of one.