The general of the sea has need of only one science, that of navigation. The one on land has need of all, or of a talent which is the equivalent of all, that will enable him to profit by all experience, and all knowledge. A general of the sea has nothing to divine. He knows where his enemy is, he knows his strength. A general on land never knows anything with certainty, never sees his enemy well, and never knows positively where he is.

The issue of a battle is the result of an instant, of a thought. There is the advance, with its various combinations, the battle is joined, the struggle goes on a certain time, the decisive moment presents itself, a spark of genius discloses it, and the smallest body of reserves accomplish victory.

Achilles was the son of a goddess and of a mortal; in that, he is the image of the genius of war. The divine part is all that that is derived from moral considerations of character, talent, the interest of your adversary, of opinion, of the temper of the soldier, which is strong and victorious, or feeble and beaten, according as he believes this divine part to be. The mortal part is the arms, the fortifications, the order of battle — everything which arises out of material things.