Titus Livius (Livy), The History of Rome, Book 1
Benjamin Oliver Foster, Ph.D., Ed.

15. From Fidenae the war-spirit, by a kind of contagion, spread to the Veientes, whose hostility was aroused by their kinship with the Fidenates, Etruscans like themselves, and was intensified by the danger which lay in their very proximity to Rome, if her arms should be directed against all her neighbours. [2] They made an incursion into Roman territory which more resembled a marauding expedition than a regular campaign; and so, without having entrenched a camp or waited for the enemy's army, they carried off their booty from the fields and brought it back to Veii. The Romans, on the contrary, not finding their enemy in the fields, crossed the Tiber, ready and eager for a decisive struggle. [3] When the Veientes heard that they were making a camp, and would be advancing against their city, they went out to meet them, preferring to settle the quarrel in the field of battle rather than to be shut up and compelled to fight for their homes and their town. [4] Without employing strategy to aid his forces, the Roman king won the battle by the sheer strength of his seasoned army, and routing his enemies, pursued them to their walls. But the city was strongly fortified, besides the protection afforded by its site, and he refrained from attacking it. [5] Their fields, indeed, he laid waste as he returned, more in [p. 57]revenge than from a desire for booty, and this disaster,¹ following upon their defeat, induced the Veientes to send envoys to Rome and sue for peace. They were deprived of a part of their land, and a truce was granted them for a hundred years.

[6] Such were the principal achievements of the reign of Romulus, at home and in the field, nor is any of them incompatible with the belief in his divine origin and the divinity which was ascribed to the king after his death, whether one considers his spirit in recovering the kingdom of his ancestors, or his wisdom in founding the City and in strengthening it by warlike and peaceful measures. [7] For it was to him, assuredly, that Rome owed the vigour which enabled her to enjoy an untroubled peace for the next forty years. [8] Nevertheless, he was more liked by the commons than by the senate, and was preeminently dear to the hearts of his soldiers. Of these he had three hundred for a bodyguard, to whom he gave the name of Celeres,² and kept them by him, not only in war, but also in time of peace.