§1. To know the enemy’s plans and conceal one’s own has the greatest importance for victory. And scarcely anyone has been defeated in war except one who was ignorant of the enemy’s design. Tomombeius lost a most valiant army and was stripped of his kingdom for almost this very reason: all his plans were betrayed.
To have known the enemy’s plans is almost to have conquered. Fulvius Nobilior learned that the enemy would seize the rear of the column. He ordered the strongest legion to march first and the baggage to follow. The enemy, enticed by the opportunity, plundered the baggage. But Fulvius had directed five cohorts of the legion to the right and five to the left of the road, and they cut down the occupied enemy. Iphicrates did the same in a not dissimilar manner. Epaminondas said that nothing in a commander was more praiseworthy than to know the enemy’s plans.
§2. Even amid military disturbance and slaughter, Germanicus had scouts among the Germans. Tacitus, Annals, book 1: “A longer route having been selected, the other things were hastened; for scouts had reported that that night was festive among the Germans and sportful with solemn banquets.”
§3. Great kings sometimes go at their own peril to various places in order to learn the enemy’s equipment. Saladin, hearing of the Christians’ equipment, traveled through Germany, the Gauls, and Spain. Egnatius, book 9, chapter 8. More prudent in this class of action was Memnon, who sent another man with his envoy, namely a famous lyre-player to whom a multitude flocked. Polyaenus, book 5.
§4. Much less should the fortune of one’s own army be unknown, for this has sometimes brought destruction. Indeed, men within the same army sometimes do not know the fortune of its parts. Brutus was victorious, while Cassius was defeated upon his own wing; and because Cassius thought that Brutus too had been defeated, he brought death upon himself. When the king of France had defeated the Swiss in Insubria, some intact formations of the Swiss thought that their own men were victorious, and on account of that error almost the whole army perished.
§5. Scouts must always be sent, but cautiously, lest after being intercepted and tortured they disclose your plans. Heraclides, under the appearance of a deserter, burned the Rhodians’ dockyards.
§6. Every means, and sometimes novel stratagems, must be employed so that scouts may be discovered. When scouts were in the army of Chares, he ordered each man to seize the man nearest him and ask him his formation, standard, maniple, and mess-company. Since the scouts could not answer these questions, they were discovered. When Theognis ordered all to put on their own arms, he discovered the scouts. But when they hide among baggage-servants and merchants, those men too must be examined, for they are generally known by someone.
§7. Secret characters in letters, whether written upon the carrier’s body or in some other manner, are now generally discovered. The safest course is to agree upon the characters before the parties are separated. Formerly, a Carthaginian wrote the secrets of the Romans upon a tablet covered with wax and sent them to his homeland. Demaratus the Greek gave warning of Xerxes’ expedition. Gellius, book 17, chapter 9, says that letters inscribed upon heads whose hair had been shaved with a razor, and then concealed by the same hair after it had grown again, were sent to friends.
The Spartan scytale is made with remarkable art. Each party has a piece of wood of the same shape and size. A long strip of paper, like a strap, is wound around it and is then written upon. The recipient winds it around his own piece of wood, and it will reproduce the same conjunction of letters that was upon the first piece of wood. Nor can an enemy draw out any meaning unless he has learned the size of the pieces of wood.
Philip, most cunning of kings, wrote a letter to Antipater: “The Thracians have rebelled; come, leaving everything.” When the Athenians intercepted it, supposing that they had received the secrets of the Macedonians and being free from concern, they withdrew their fleet. Philip’s commanders passed over with no one opposing them.
There is indeed a great opportunity to delude the enemy if fictitious commands are sent to commanders. Yet to recognize them and distinguish the true from the fictitious will not be difficult if some sign known to them alone is added. Mendoza relates that during a siege a sheet enclosed in lead was given to two men, which they swallowed. The sheet was written in such a way that they themselves did not know its contents and could not disclose them even under torture; but they came to the enemy under the appearance of deserters.
Men not only intercept letters sent to allies, but also direct purported letters of the enemy to the enemy by imitating the seal and handwriting, so that they may afflict them with some error. They are accustomed to write letters for the punishment of deserters which are intended to be intercepted, so that the deserters’ credit among the enemy may be destroyed and they may appear to be scouts. Conon, abandoned by his allies, sent a deserter to report that they were fleeing. When the allies perceived men lying in wait, they returned.
§8. Every method of messengers and letters pertains to reconnaissance. Necessity has devised various ways of sending out messengers and delivering letters. Pontius Cominus lowered himself down the Tarpeian Rock and, after swimming across the Tiber, arrived at Veii; afterward he returned unharmed to the Capitol. A Campanian soldier carried a letter enclosed in his belt to the Carthaginians. Letters are also enclosed in the inner part of scabbards. By letters sent upon arrows and by persuading captives that he was coming to liberate the state of the Troezenians, Cleonymus fell upon them while they were divided.
Caesar’s messenger hurled letters into the camp, but there is a danger that they may not be noticed. Therefore, they are better sent through men secretly instructed for the purpose—through those who bring hay, straw, fruit, and similar things into camps. Letters are easily carried by unknown and lowly men. Eric, king of Sweden, wooed the queen of England by letters enclosed in a staff, but the Danish commander intercepted them. Harpagus inserted a letter into a hare.
§9. Scipio followed a remarkable method of reconnaissance. When Laelius was sent as envoy to Syphax, Scipio sent with him, in the place of servants, the choicest tribunes and centurions. Chasing a horse which had been let loose through the camp, they saw all its fortifications and obtained an easy victory for Scipio. The Carthaginians ordered Hamilcar to go to Alexander under the appearance of an exile and report Alexander’s plans to them. The same was also done with the Romans. Cato interrogated one enemy whom he had seized and tortured concerning the enemy’s plans. This is uncertain, since few generally know them.
In this matter, however, the greatest sagacity and the greatest prudence are needed. When Paulus Aemilius saw a great multitude of birds fly out of a forest all at once, he did not groundlessly judge that an ambush of Etruscans was there. By the same sign Tisamenus, son of Orestes, learned that the ridge was occupied by the enemy.
The Carthaginians seem to me to have signaled from a distance most expediently of all. For they could give a signal such that whatever was lacking could be seen at Carthage. They had made two water clocks of equal size and had also established rings at equal intervals. Upon these they had inscribed various things which they might at some time require—for example, engines, gold, grain, cavalry, and infantry. If, therefore, they requested any one of these things, when the water had descended to the ring upon which that thing was inscribed they kindled a fire. Upon seeing this and inspecting their own water clock, assistance was sent from Carthage.
Two things had to be diligently observed in this matter: first, that diligent account be taken of the turning of the water clocks; second, that the fire be made in a fixed manner and place, lest, if there were some accidental or hostile fire in the vicinity, the senate should think that assistance was being requested.
When letters are sent by pigeons, care must be taken lest the birds fall into the enemy’s hands, as happened to the sultan while the Christians were besieging Ptolemais. When a signal is given by fires, contrary fires must be kindled so that the enemy may doubt whose they are. The Plataeans did this while they were being besieged by the Spartans. The enemy is especially deceived by changing signals. When the Arabs used smoke by day and fires by night to signify that enemies were approaching, they did this for successive days; but when the enemy was present, they deliberately omitted the signals. Since that omission was itself the signal to them, the enemies, thinking that they lay concealed, conducted everything with greater confidence.