Sextus Iulius Frontinus, vir consularis de re militari

...and they are divided. They will have gratitude if they are of their species, and the force of their grace, once placed in art and skill, benefits both where the enemy is to be avoided and where he is to be crushed. In this matter, since the effect of words also proved illustrious, we have placed examples of things said just as we have of things done.

The types of these which instruct a commander in those things that are to be conducted before battle:

On concealing plans. Chapter I.
On exploring the plans of the enemy. Chapter II.
On establishing the state of war. Chapter III.
On leading the army through places hostile to the enemy. Chapter IV.
On escaping from very difficult places. Chapter V.
On ambushes made during a march. Chapter VI.
How those things in which we are deficient may appear not to be lacking, so that their use may be satisfied. Chapter VII.
On distinguishing between enemies. Chapter VIII.
On suppressing the sedition of soldiers. Chapter IX.
How untimely demands for battle may be inhibited. Chapter X.
How an army should be incited to battle. Chapter XI.
On dissolving the fear that causes soldiers to succumb to adverse omens. Chapter XII.

On concealing plans. Chapter I.

Marcus Portius Cato, thinking that the conquered cities of Spain would rebel in time due to the confidence they placed in their walls, wrote to each of them separately ordering them to destroy their fortifications. He threatened war unless they complied immediately, and he ordered the letters to be delivered to all the cities on the same day. Each of the cities believed the command was issued to it alone. A conspiracy could have made them defiant if it had been known that the same thing was announced to all. Hamilcar, leader of the Carthaginians, in order to land his fleet unexpectedly in Sicily, did not announce where he was going. Instead, he gave sealed tablets to all his captains, in which it was written which part he wished to target. He ordered that no one should read them unless they were driven off course from the flagship by the force of a storm. Caius Lelius, having set out to Syphax, took with him some tribunes and centurions as scouts, under the guise of servants and attendants. Among these was L. Statorium, whom some of the enemy thought they recognized because he had been in those same camps before. To conceal his status, Lelius beat him with a stick as if he were a servant. Tarquinius Superbus...