DURING our stay at Sobral(de Monte Agraço)I saw another artifice employed by the English, and one of sufficient importance to be worth noting. It is often said that thoroughbred horses are of no use in war, because their price is so high and they require so much care that it would be almost impossible to provide a squadron, much more a regiment, with them. Nor indeed do the English use them on campaign; but they have a habit of sending single officers, mounted on fast thoroughbreds, to watch the movements of a hostile army. These officers get within the enemy's cantonments, cross his line of march, keep for days on the flanks of his columns, always just out of range, till they can form a clear idea of his number and the direction of his march.
After our entry into Portugal, we frequently saw observers of this kind flitting round us. It was vain to give chase to them, even with the best-mounted horsemen. The moment the English officer saw any such approach he would set spurs to his steed, and nimbly clearing ditches, hedges, even brooks, he would make off at such speed that our men soon lost sight of him, and perhaps saw him soon after a league further on, note-book in hand, at the top of some hillock, continuing his observations.
This practice, which I never saw anyone employ like the English, and which I tried to imitate during the Russian campaign, might perhaps have saved Napoleon at Waterloo by affording him a warning of the arrival of the Prussians. Anyhow, these English 'runners', who were the despair of the French general from the moment we left Spain, increased in boldness and cunning as soon as we were in front of Sobral. One could see them come out of the lines and race with the speed of stags through the vines and over the rocks to inspect the positions occupied by our troops.
- The Memoirs of Baron de Marbot - Volume II - Chapter XV