The campaign of Talavera may in some sense be called a failure; it was too soon to attempt to shake the French hold on Spain, though Wellington may be excused for the mistake. The magnificent defence of Saragossa had created a great sensation; there was no doubt Spaniards could fight. No one could have imagined the ignorance and the irrational pride of their commanders, or the amazing assurance with which government and generals alike gave elaborate undertakings which they never meant to fulfil. At the same time the slaughter of Talavera was not wasted: the victory gave the English cabinet, and still more the nation, confidence alike in their general and in his troops. Talavera was the first distinct defeat sustained by a French army of any size since Napoleon had appeared on the scene.[68] Wellington had two long years of severe struggle before the tide began to flow in his favour, contending at once with the far superior strength of the French and with half-heartedness at home; it may be doubted whether, without Talavera to his credit, he would have successfully overcome these difficulties. In 1810 Napoleon gave the chief command to Massena, the ablest of his marshals with one possible exception, the only one who had gained distinction at the head of an independent army. Massena's instructions were, in one of Napoleon's pet phrases, to drive the English into the sea, and the emperor, who could estimate no forces that could not be expressed in battalions, had every reason to expect that he would achieve his task. Wellington's scheme of defence was based on the geographical conditions. Three important rivers flow out of Spain across Portugal into the Atlantic. Where the Guadiana crosses the frontier stands the great fortress of Badajos on the Spanish side, faced by Elvas on the Portuguese. As both were at this time in the hands of the allies (Elvas indeed remained so throughout) they formed a serious obstacle to an attack on Portugal from this direction. Moreover it was obviously absurd for Massena to base his attack on the south, lengthening his communications by hundreds of miles: all that was possible was a subsidiary attack from the French army in Andalusia, already fully occupied with the hopeless siege of Cadiz. The Tagus valley is narrow, and barren of supplies, and almost as circuitous a route from France as the Guadiana. North of the Tagus, the Sierra de Estrella, which is a sort of continuation of the Sierra de Guadarrama, though at an angle to it, lies behind the frontier between Spain and Portugal. The roads across it into the Tagus basin were few and bad, and Wellington took care to render them worse. Thus the only route that needed serious defence was the northern one by the broad valley of the Douro, the natural and obvious course for an invader based on France, the easiest for an army, though not the shortest, between Lisbon and Madrid. Here also two fortresses faced each other across the frontier,