Nor can that knowledge of countries which I have spoken of as necessary in a commander, be obtained in any convenient way except by the chase.  For he who joins therein gains a special acquaintance with the character of the country in which it is followed; and he who has made himself specially familiar with one district, will afterwards readily understand the character of any strange country into which he comes.  For all countries, and the districts of which they are made up, have a certain resemblance to one another, so that from a knowledge of one we can pass easily to the knowledge of another.  He therefore who is without such practical acquaintance with some one country, can only with difficulty, and after a long time, obtain a knowledge of another, while he who possesses it can take in at a glance how this plain spreads, how that mountain slopes, whither that valley winds, and all other like particulars in respect of which he has already acquired a certain familiarity.

The truth of what I affirm is shown by Titus Livius in the case of Publius Decius, who, being military tribune in the army which the consul Cornelius led against the Samnites, when the consul advanced into a defile where the Roman army were like to be shut in by the enemy, perceiving the great danger they ran, and noting, as Livius relates, a hill which rose by a steep ascent and overhung the enemy’s camp, and which, though hard of access for heavy-armed troops, presented little difficulty to troops lightly armed, turned to the consul and said:—­“Seest thou, Aulus Cornelius, yonder height over above the enemy, which they have been blind enough to neglect?  There, were we manfully to seize it, might we find the citadel of our hopes and of our safety.” Whereupon, he was sent by the consul with three thousand men to secure the height, and so saved the Roman army.  And as it was part of his plan to make his own escape and carry off his men safely under shelter of night, Livius represents him as saying to his soldiers:—­“Come with me, that, while daylight still serves, we may learn where the enemy have posted their guards, and by what exit we may issue hence.” Accordingly, putting on the cloak of a common soldier, lest the enemy should observe that an officer was making his rounds he surveyed their camp in all directions.

Now any one who carefully studies the whole of this passage, must perceive how useful and necessary it is for a captain to know the nature of places, which knowledge had Decius not possessed he could not have decided that it would be for the advantage of the Roman army to occupy this hill; nor could he have judged from a distance whether the hill was accessible or no; and when he reached the summit and desired to return to the consul, since he was surrounded on all sides by the enemy, he never could have distinguished the path it was safe for him to take, from those guarded by the foe.  For all which reasons it was absolutely essential that Decius should have that thorough knowledge which enabled him by gaining possession of this hill to save the Roman army, and to discover a path whereby, in the event of his being attacked, he and his followers might escape.