Now, first, it so happened, unluckily for this lucid military notion of Portugal, that in Massena’s invasion lord Wellington stopped to fight on the mountain of Busaco, and stopped Massena altogether at the mountains of Alhandra, Aruda, Sobral, and Torres Vedras—in other words at the lines, and that he did not once stop him or attempt to stop him by defending a river. That Massena, in his retreat, stopped lord Wellington on the mountain of Santarem, attempted to stop him on the mountains of Cazal Nova, Moita, and Guarda, but never attempted to stop him by defending a river, save at Sabugal, and then he was instantly beaten. Oh, certainly, ’tis a most noble general, and a very acute critic! Nevertheless, I must support my own opinions about the frontier of Portugal, the non-necessity of invading this country in one mass, and the unfordable nature of the Tagus, by the testimony of two generals as distinguished as honest Iago.
Extract of a letter from sir John Moore.
‘I am not prepared at this moment to answer minutely your lordship’s question respecting the defence of Portugal; but I can say generally that the frontier of Portugal is not defensible against a superior force. It is an open frontier, all equally rugged, but all equally to be penetrated.’
Extracts from lord Wellington’s Correspondence.
‘In whatever season the enemy may enter Portugal, he will probably make his attack by two distinct lines, the one north the other south of the Tagus; and the system of defence must be founded upon this general basis. In the summer season, however, the Tagus being fordable, &c. &c., care must be taken that the enemy does not by his attack directed from the south of the Tagus and by the passage of that river, cut off from Lisbon the British army engaged in operations to the north of the Tagus.’
‘The line of frontier to Portugal is so long in proportion to the extent and means of the country, and the Tagus and the mountains separate the parts of it so effectually from each other, and it is so open in many parts, that it would be impossible for an army acting upon the defensive to carry on its operations upon the frontier without being cut off from the capital.’
‘In the summer it is probable as I have before stated that the enemy will make his attacks in two principal corps, and that he will also push on through the mountains between Castello Branco and Abrantes. His object will be by means of his corps, south of the Tagus, to turn the positions which might be taken in his front on the north of that river; to cut off from Lisbon the corps opposed to him; and to destroy it by an attack in front and rear at the same time. This can be avoided only by the retreat of the right centre and left of the allies, and their junction at a point, at which from the state of the river they cannot be turned by the passage of the Tagus by the enemy’s left. The first point of defence which presents itself below that at which the Tagus ceases to be fordable, is the river Castenheira close to the lines.’
In the above extracts, the fordable nature of the Tagus has been pretty clearly shown, but I will continue my proofs upon that fact to satiety.
Lord Wellington to Charles Stuart, Esq.
‘The line of operations which we are obliged to adopt for the defence of Lisbon and for our own embarkation necessarily throws us back as far as below Salvaterra on the Tagus, to which place, and I believe lower, the Tagus is fordable during the summer; and we should be liable to be turned or cut off from Lisbon and the Tagus if we were to take our line of defence higher upon the river.’