The History of Rome (1.14.3-1.14.7)

Romulus is reported to have been less distressed at this incident than his position demanded, either because of the insincerity inherent in all joint sovereignty, or because he thought he had deserved his fate.

He refused, therefore, to go to war, but that the wrong done to the ambassadors and the murder of the king might be expiated, the treaty between Rome and Lavinium was renewed. Whilst[*] in this direction an unhoped-for peace was secured, war broke out in a much nearer quarter, in fact almost at the very gates of Rome. The people of Fidenae considered that a power was growing up too close to them, so to prevent the anticipations of its future greatness from being realised, they took the initiative in making war.

Armed bands invaded and devastated the country lying between the City and Fidenae. Thence they turned to the left-the Tiber barred their advance on the right-and plundered and destroyed, to the great alarm of the country people.

A sudden rush from the fields into the City was the first intimation of what was happening.

A war so close to their gates admitted of no delay, and Romulus hurriedly led out his army and encamped about a mile from Fidenae. Leaving a small detachment to guard the camp, he went forward with his whole force, and whilst one part were ordered to lie in ambush in a place overgrown with dense brushwood, he advanced with the larger part and the whole of the cavalry towards the city, and by riding up to the very gates in a disorderly and provocative manner he succeeded in drawing the enemy.