Nevertheless, war as a science must be worse than useless, unless its underlying principles have universal application. Nor is it maintained that there were no circumstances which would have justified a departure from the usually defensive policy of the Confederates. Upon two occasions the main army of the South, having successfully encountered upon its own soil the most prodigious efforts of the enemy's strength, sought to follow him in the moment of his recoil. The Confederate invasion of 1862, culminating at Antietam, and that of 1863, culminating at Gettysburg, were undertaken with the purpose of destroying, upon his own soil, an enemy already defeated. Each of these endeavors was based upon sound principles; and there is no little palliation for the disaster, in either case, in reflecting how great would have been the results of success. Much of the philosophy of the war in Virginia is to be explained by the fact of the thoroughly aggressive character, as soldiers, of President Davis and General Lee. These two directing minds, by whose combined genius and will, the fortunes of the Confederacy were so long upheld, in full and cordial coöperation during the entire war, were in nothing more harmonious, than in the desire for an aggressive campaign, whenever it could be undertaken with a reasonable promise of success. Hence, the history of the army of Northern Virginia develops, throughout, that military policy which is known as the "defensive with offensive returns." After the conclusion of the alliance between Virginia and the Confederate States, which placed all "military operations, offensive and defensive, in Virginia," under the control of the Confederate President, troops from the other Southern States had been thrown northward with astonishing rapidity. As rapidly as they arrived, regiments were sent to the various localities where it had been thought expedient to establish a defensive force. These posts were distributed with a view to their strategic bearing upon particular sections of territory, which it was deemed necessary to defend, and also with reference to their strategic connection with each other, and with the chain of combinations making the general plan of defense.