As the day of battle draws to a close and the decision has taken place, the _victorious attacker_ has generally accomplished a long march to the battlefield and carried out an exceedingly exhausting attack. The troops have perhaps all been employed in the battle, down to the last reserve. Ammunition, food, and water are often lacking. It is therefore quite natural that the mere physical energy required for a pursuit is wanting. If, on the other hand, the _defender_ is successful, it is generally against a superior enemy, or one that is thought to be superior. With the greatest expenditure of moral and physical force he has held his own. In the evening of the day of battle, when the attacks cease, he is still perhaps scarcely conscious of his victory, and still imagines that the enemy is endeavouring to turn his flank. He awaits renewed onslaughts, and will be fearful of imperilling his success by leaving the positions which he has maintained with such difficulty, in order, on his side, to take up the offensive. It is therefore but natural that a pursuit should at first remain in abeyance. If, however, it is not carried out at once, the favourable opportunity is generally lost forever.
The _beaten defender_, on the other hand, has often still a surplus of fresh troops. On the day of battle he will generally have had no exhausting marches to undertake. The battle has not imposed nearly such heavy physical demands upon him as upon the attacker. He has also been able to supply himself during the fight much better than the latter. To these factors of advantage must be added the instinct of self-preservation of the individual, which continually induces afresh the desire to escape from the grasp of the enemy. What can be more natural for the beaten defender after a lost battle than to march long distances, and thus successfully to evade pursuit, unless it be immediately undertaken? General von Goeben gave orders on the evening of the battle of St. Quentin that all troops must march five miles[42] the next day. But the French had already covered a similar distance during the night, and were no longer within reach.
The _beaten attacker_ also may, after the battle, no longer have at his disposal sufficient physical force to carry out a further immediate march, but, as _before_ the fight he was in superior force, or considered himself to be so, it will not be necessary for him to withdraw from the enemy as quickly as a beaten defender. The reason for this lies in the difficulty which exists for the latter of taking up the pursuit. The attacker can then utilise the time after the battle to secure himself in the terrain and to re-form his units. He falls back on his reserves of supply and ammunition. Unless he has suffered a destructive defeat, the pursuer will generally find him the next morning again in a condition to offer some resistance.