Titus Livius (Livy), The History of Rome, Book 26
D. Spillan, A.M., M.D., Cyrus Evans, Ed.

4. Meanwhile all the strength of the war was directed against Capua. It was, however, more strictly blockaded than besieged. The slaves and populace could neither endure the famine, nor send messengers to Hannibal through guards so [p. 1022]closely stationed. [2] A Numidian was at length found, who, on undertaking to make his way with it, was charged with a letter; and going out by night, through the midst of the Roman camp, in order to fulfil his promise, he inspired the Campanians with confidence to try the effect of a sally from every quarter, while they had any strength remaining. [3] In the many encounters which followed, their cavalry were generally successful, but their infantry were beaten: however, it was by no means so joyful to conquer, as it was miserable to be worsted in any respect by a besieged and almost subdued enemy. A plan was at length adopted, by which their deficiency in strength might be compensated by stratagem. [4] Young men were selected from all the legions, who, from the vigour and activity of their bodies, excelled in swiftness; these were supplied with bucklers shorter than those worn by horsemen, and seven javelins each, four feet in length, and pointed with steel in the same manner as the spears used by light-armed troops. [5] The cavalry taking one of these each upon their horses, accustomed them to ride behind them, and to leap down nimbly when the signal was given. [6] When, by daily practice, they appeared to be able to do this in an orderly manner, they advanced into the plain between the camp and the walls, against the cavalry of the Campanians, who stood there prepared for action. [7] As soon as they came within a dart's cast, on a signal given, the light troops leaped down, when a line of infantry formed out of the body of horse suddenly rushed upon the cavalry of the enemy, and discharged their javelins one after another with great rapidity; which being thrown in great numbers upon men and horses indiscriminately, wounded a great many. [8] The sudden and unsuspected nature of the attack, however, occasioned still greater terror; and the cavalry charging them, thus panic-struck, chased them with great slaughter as far as their gates. [9] From that time the Roman cavalry had the superiority; and it was established that there should be velites in the legions. [10] It is said that Quintus Navius was the person who advised the mixing of infantry with cavalry, and that he received honour from the general on that account.