Only from those points onward is it possible for an army to live on the local produce: in the upland it must carry its food with it; for a single division would exhaust in a day the stores of the poor villages of the mountains; and the small poverty-stricken towns of Guarda, Celorico, Sabugal, Penamacor, and Idanha have few resources. Castello Branco and Vizeu are the only two places in the upland where there is a valley of some breadth and richness, which can supply an army for many days. In this simple fact lies the explanation of the difficulties of the Portuguese campaigns of 1810 and 1811. Both the invader and the defender must bring their food with them, and protracted operations can only be kept up by means of incessant convoys from the rear. The campaign not infrequently became a starving-match, and the combatant who first exhausted his provisions had to retire, and to disperse his divisions in search of the wherewithal to live. Thanks to Wellington’s providence it was always the French who were forced to this expedient. [155] So much so that in _Corresp._, xx. p. 552, we find him informing Masséna that Badajoz and Elvas need not be touched till after Lisbon has fallen. The first contrary view, ordering a demonstration on the Lower Tagus, appears in the dispatch on p. 273 of vol. xxi. The Beira frontier is divided into two sections by the range of mountains which crosses the border at right angles, half way between Douro and Tagus: it is known as the Sierras de Gata and de Jarama while in Spain, as the Serra da Estrella when it reaches Portugal. Its central ganglion lies between the high-lying towns of Sabugal and Penamacor in Portugal and the pass of Perales in Spain. From this point run off the great spurs which separate the valleys of the Ponçul, the Zezere, the Agueda, the Coa, and the Alagon. An invader must make his choice whether he will advance into Portugal south or north of the Serra da Estrella: to attempt to do so on both sides of the range would be risking too much, if there is an enemy of any strength in the field, since the columns to the right and to the left would be hopelessly separated, and liable to be beaten in detail. In the whole Peninsular War there was only one invasion made by the southern route, that of Junot in the winter of 1807-8. It was successful because it was absolutely unopposed. Nevertheless the French lost many men, had to leave their artillery behind them, and only arrived with the shadow of an army at Abrantes. It is true that Junot chose absolutely the worst path that could be found between the Serra da Estrella and the Tagus--the pass of Rosmarinhal, close above the latter river--and that he would have fared not quite so badly if he had marched from Zarza on Idanha and Castello Branco. But even at the best this region is most inhospitable: there are points where water is not procurable on stretches of eight or ten miles, others