De Brack and many other writers make it plain that whilst from 1805 up to, perhaps, 1812 information was easily gained by the French cavalry for Napoleon, later a complete change came over the scene, and the Cossacks, overrunning the country, picketed the French columns. Perhaps the natives were weary of French exactions, but in any case the result is said to have been that “the genius of the Emperor was paralysed by the activity of the Cossacks.” We have at least four or five instances where one side’s light cavalry or guerrillas “paralysed the genius” of the other’s generals by gaining superiority in the outposts, or, rather, anywhere outside their opponent’s outposts: (_a_) in 1812, 1813, 1814; (_b_) in the Peninsular War; (_c_) in the early part of the American Civil War; (_d_) in the South African War; and (_e_) in the Manchurian War. With these examples before us it must become a serious factor in taking thought for a campaign, how far the cavalry will be able to effect this. Our training must be such as to enable us to play this part, of picketing the enemy, if possible; certainly we should do so in a friendly country.[61] We know it is usually only done by the side which has a knowledge of the country; but may not the almost universal knowledge of map-reading in the cavalry and a good supply of maps obviate this? But let us remember above all things that nothing will be done in war which has not by constant practice become a second nature in peace. Let us then practise not only our officers, but our men, in picketing every large body of troops which train within fifty miles of us. Often C.O.’s, shortsightedly we think, do not welcome the attention of cavalry thus picketing them; but even if this is the case, it may still be practised by our cavalry, but in a way which does not draw attention to the fact--the training will be none the worse, and (though perhaps hardly in this sense) the “offensive spirit” must be second nature to us.[62] The instruction of cavalry in outpost work is difficult, because in the first place many parts of the duty make great demands on the instructor’s imagination, powers of explanation, and what we may call ability for stage management.