I. When an army awaits the attack, it takes its position and forms its line of battle according to the nature of the ground and the supposed character and strength of the enemy's forces. Such is usually the case when an army wishes to cover a siege, protect a capital, guard depots of provisions and military stores, or some important strategic point. The general relations of positions with strategy and engineering have already been considered; we will now discuss merely their relations to battles. The first condition to be satisfied by a tactical position is, that its debouches shall be more favorable for falling on the enemy when he has approached to the desired point, than those which the enemy can have for attacking our line of battle. 2d. The artillery should have its full effect upon all the avenues of approach. 3d. We should have good ground for manoeuvring our own troops unseen, if possible, by the enemy. 4th. We should have a full view of the enemy's manoeuvres as he advances to the attack. 5th. We should have the flanks of our line well protected by natural or artificial obstacles. 6th. We should have some means of effecting a retreat without exposing our army to destruction. It is very seldom that all these conditions can be satisfied at the same time; and sometimes the very means of satisfying one, may be in direct violation of another. A river, a forest, or a mountain, which secures a flank of a line of battle, may become an obstacle to a retreat, should the defensive forces be thrown back upon that wing. Again, the position may be difficult of attack in front or on the wings, and at the same time unfavorable for retreat. Such was Wellington's position at Waterloo. The park of Hougomont, the hamlet of Haye Sainte, and the marshy rivulet of Papelotte, were serious obstacles against the attacking force; but the marshy forest of Soignies in rear, with but a single road, cut off all hope of retreat. II. According to the strategic relations of the contending forces in a campaign, will it be determined whether we are to await the enemy, or to seek him out and attack him wherever he may be found. We may sometimes be obliged to make the attack at all hazards, for the purpose of preventing the junction of two corps, or to cut off forces that may be separated from the main body by a river, &c. As a general rule the attacking force has a moral superiority over the defensive, but this advantage is frequently more than counterbalanced by other conditions.