Massena entered Portugal with sixty-five thousand men, his reenforcements while at Santarem were about ten thousand, and he repassed the frontier with forty-five thousand ; hence the invasion of Portugal cost him about thirty thousand men, of which fourteen thousand might have fallen by the sword or been taken.
Not more than six thousand were lost during the retreat; but had Lord Wellington, unrestrained by political considerations, attacked him vigorously at Redinha, Condeixa, Casal Nova, and Miranda de Corvo, half the French army would have been lost. It is unquestionable that a retreating army should fight as little as possible.
When the French reached the Agueda, their cavalry detachments, heavy artillery, and convalescents, again augmented the army to more than fifty thousand men, but the fatigues of the retreat and the want of provisions would not suffer them to show a front to the allies; wherefore, drawing two hundred thousand rations from Ciudad, they fell back to Salamanca, and Lord Wellington invested Almeida.
The light division occupied Gallegos and Espeja, the rest of the army were disposed in villages on both sides of the Coa, and the head-quarters were transferred to Villa Formosa.
Here Colonel Waters, who had been taken near Belmonte during the retreat, rejoined the army. Confident in his own resources, he had refused his parole, and, when carried to Ciudad Rodrigo, rashly mentioned his intention of escaping to the Spaniard in whose house he was lodged.
This man betrayed him, but a servant, detesting his master's treachery, secretly offered his aid; Waters only desired him to get the rowels of his spurs sharpened, and when the French army was near Salamanca, he being in the custody of gendarmes, waited until their chief, who rode the only good horse in the party, had alighted, then giving the spur to his own beast, galloped off!
An act of incredible resolution and hardihood, for he was on a large plain, and before him, and for miles behind him, the road was covered with the French columns.
His hat fell off, and, thus distinguished, he rode along the flank of the troops, some encouraging him, others firing at him, and the gendarmes, sword in hand, close at his heels; nevertheless he broke at full speed, between two columns, gained a wooded hollow, and, having baffled his pursuers, evaded the rear of the enemy's army.
The third day he reached head-quarters, where Lord Wellington had caused his baggage to be brought, observing that he would not be long absent!
History of the War in the Peninsula and in the South of France
from A.D. 1807 to A.D. 1814
By Sir William Francis Patrick Napier