The art of war owes its origin and growth to the deeds of a few great captains. Not to their brilliant victories; not to the noble courage evoked by their ambition; not to their distortion of mechanics and the sciences into new engines of slaughter; not to their far-reaching conquests; but to their intellectual conceptions. For war is as highly intellectual as astronomy. The main distinction between the one and the other lies in the fact that the intellectual conception of the general must at once be so put into play as to call for the exertion of the moral forces of his character, while the astronomer’s inspiration stops at a purely mental process. What has produced the great captains is the coexistence of extraordinary intellect and equal force of character, coupled with events worthy of and calling out these qualities in their highest expression. My effort will be to suggest how, out of the campaigns and battles of the great captains, has arisen what to-day we call the art of war,--not so much out of the technical details, which are a subordinate matter, as the general scheme; and to show that, while war is governed by its rules as well as art, it is the equipment of the individual which makes an Alexander or a Michael Angelo. Six of these captains stand distinctly in a class by themselves, far above any others. They are, in ancient days, Alexander, Hannibal, Cæsar,--all within three hundred years of each other. Then follows a gap of seventeen centuries of unmethodical war, and we complete the list with Gustavus Adolphus, Frederick, and Napoleon,--all within two centuries. “The art of war is the most difficult of all arts, the military reputation in general the greatest of all reputations,” says Napoleon. The limited number of great captains proves this true. The words _campaign_ and _battle_ cover the same ground as _strategy_ and _tactics_. Let me make these plain to you, and I shall have done with definitions and technicalities. A campaign consists in the marching of an army about the country or into foreign territory to seek the enemy or inflict damage on him. Strategy is the complement of this term, and is the art of so moving an army over a country,--on the map, as it were,--that when you meet the enemy you shall have placed him in a disadvantageous position for battle or other manœuvres. One or more battles may occur in a campaign. Tactics (or grand tactics, to distinguish the art from the mere details of drill) relates only to and is coextensive with the evolutions of the battle-field. Strategy comprehends your manœuvres when not in the presence of the enemy; tactics, your manœuvres when in contact with him. Tactics has always existed as common military knowledge, often in much perfection. Strategy is of modern creation, _as an art which one may study_. But all great captains have been great strategists.