_Defensive_ battles, or those given in a chosen position by an army waiting the attack of the enemy.2d._Offensive_ battles, or those made by an army which attacks the enemy in position.3d.The _mixed_ or _unforeseen_ battles, given by two armies meeting while on the march.
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.