4.5
If your route lies in dangerous country, a prudent commander will have a second advanced guard ahead of his scouts for reconnaissance purposes. For it is useful both for attack and defence to discover an enemy as far off as possible. It is useful also to halt at the passage of a river, that the rear guard may not wear out their horses in chasing their leader. These rules, no doubt, are familiar to nearly everybody; but few will take the trouble to observe them.
4.6
A cavalry commander should be at pains even in time of peace to acquaint himself with hostile and friendly country alike. In case he is without personal experience, he should at least consult the men in the force who have the best knowledge of various localities. For the leader who knows the roads has a great advantage over one who does not. In making plans against the enemy, too, a knowledge of the district makes a great difference.
4.7
You must also have taken steps to enlist the services of spies before the outbreak of war. Some of these should be citizens of neutral states, and some merchants, since all states invariably welcome the importer of merchandise. Sham deserters, too, have their use on occasions.
4.8
Still, you must never neglect to post guards through reliance on spies; on the contrary, your precautions must at all times be as complete as when you have information that the enemy is approaching. For even if the spies are entirely reliable, it is difficult to report at the critical moment, since many things happen in war to hinder them.
