Titus Livius (Livy), The History of Rome, Book 5
Rev. Canon Roberts, Ed.

43. For¹ some days the Gauls had been making useless war merely upon the houses of the City. Now that they saw nothing surviving amidst the ashes and ruin of the captured City except an armed foe whom all these disasters had failed to appal, and who would entertain no thought of surrender unless force were employed, they determined as a last resort to make an assault on the Citadel. [2] At daybreak the signal was given and the whole of their number formed up in the Forum. Raising their battle-shout and locking their shields together over their heads, they advanced. The Romans awaited the attack without excitement or fear, the detachments were strengthened to guard all the approaches, and in whatever direction they saw the enemy advancing, there they posted a picked body of men and allowed the enemy to climb up, for the steeper the ground they got on to, the easier they thought it would be to fling them down the slope. [3] About midway up the hill the Gauls halted; then from the higher ground, which of itself almost hurled them against the enemy, the Romans charged, and routed the Gauls with such loss and overthrow that they never again attempted that mode of fighting either with detachments or in full strength. [4] All hope, therefore, of forcing a passage by direct assault being laid aside, they made preparations for a blockade. Up to that time they had never thought of one; all the corn in the City had been destroyed in the conflagrations, whilst that in the fields around had been hastily carried off to Veii since the occupation of the City. [5] So the Gauls decided to divide their forces; one division was to invest the Citadel, the other to forage amongst the neighbouring States so that they could supply corn to those who were keeping up the investment.

It² was [6??] Fortune herself who led the Gauls after they left the City to Ardea, that they might have some experience of Roman courage. [7] Camillus was living there as an exile, grieving more over his country's fortunes than his own, eating his heart out in reproaches to gods and men, asking in indignant wonder where the men were with whom he had taken Veii and Falerii; men whose valour in all their wars was greater even than their success. [8] Suddenly he heard that the Gaulish army was approaching, and that the Ardeates were engaged in anxious deliberation about it. He had generally avoided the council meetings, but now, seized with an inspiration nothing short of divine, he hastened to the assembled councillors and addressed them as follows: