There are two kinds of positions,--the _strategic_, which has been discussed in Article XX., and the _tactical_. The latter, again, are subdivided. In the first place, there are intrenched positions occupied to await the enemy under cover of works more or less connected,--in a word, intrenched camps. Their relations to strategic operations have been treated in Article XXVII., and their attack and defense are discussed in Article XXXV. Secondly, we have positions naturally strong, where armies encamp for the purpose of gaining a few days' time. Third and last are open positions, chosen in advance to fight on the defensive. The characteristics to be sought in these positions vary according to the object in view: it is, however, a matter of importance not to be carried away by the mistaken idea, which prevails too extensively, of giving the preference to positions that are very steep and difficult of access,--quite suitable places, probably, for temporary camps, but not always the best for battle-grounds. A position of this kind, to be really strong, must be not only steep and difficult of access, but should be adapted to the end had in view in occupying it, should offer as many advantages as possible for the kind of troops forming the principal strength of the army, and, finally, the obstacles presented by its features should be more disadvantageous for the enemy than for the assailed. For example, it is certain that Massena, in taking the strong position of the Albis, would have made a great error if his chief strength had been in cavalry and artillery; whilst it was exactly what was wanted for his excellent infantry. For the same reason, Wellington, whose whole dependence was in the fire of his troops, made a good choice of position at Waterloo, where all the avenues of approach were well swept by his guns. The position of the Albis was, moreover, rather a strategic position, that of Waterloo being simply a battle-ground. The rules to be generally observed in selecting tactical positions are the following:-- 1. To have the communications to the front such as to make it easier to fall upon the enemy at a favorable moment than for him to approach the line of battle. 2. To give the artillery all its effect in the defense. 3. To have the ground suitable for concealing the movements of troops between the wings, that they may be massed upon any point deemed the proper one. 4. To be able to have a good view of the enemy's movements. 5. To have an unobstructed line of retreat. 6. To have the flanks well protected, either by natural or artificial obstacles, so as to render impossible an attack upon their extremities, and to oblige the enemy to attack the center, or at least some point of the front.