Titus Livius (Livy), The History of Rome, Book 34
Cyrus Evans, Ed.

39. For some time the Lacedaemonians maintained their ground against the Romans, in the narrow passes; and three armies, on each side, fought, at one time, in different places. [2] Afterwards, when the heat of the contest increased, the contest was, by no means, an equal one: for the Lacedaemonians fought with missile arms, against which the Roman soldiers, by means of their large shields, easily defended themselves, and many of their blows either missed, or were very weak; [3] for, the narrowness of the place causing them to be closely crowded together, they neither had room to discharge their weapons with a previous run, which gives great force to them, nor clear and steady footing while they made their throw [p. 1531]Of those, therefore, discharged against the [4??] front of the Romans, none pierced their bodies, few even their shields; but several were wounded by those who surrounded them from higher places. [5] And presently, when they advanced a little, they were hurt unawares, both with javelins, and tiles also thrown from the tops of the houses. [6] On this they raised their shields over their heads; and joining them so close together as to leave no room for injury from such random casts, or even for the insertion of a javelin, by a hand within reach, they pressed forward under cover of this tortoise fence. [7] For some time the narrow streets, being thronged with a multitude of their own soldiers, and also of the enemy, considerably retarded the progress of the Romans; but when once, by gradually pushing back the enemy, they gained the wider streets of the city, the impetuosity of their attack could no longer be withstood. [8] While the Lacedaemonians, having turned their backs, fled precipitately to the higher places, Nabis, being utterly confounded, as if the town were already taken, began to look about for a way to make his escape. [9] Pythagoras, while in other respects he displayed the spirit and conduct of a general, was now the sole means of saving the city from being taken. [10] For he ordered the buildings nearest to the wall to be set on fire; and these being instantly in a blaze, those who, on another occasion, would have brought help to extinguish the fire, now helping to increase it, the roofs tumbled on the Romans; [11] and not only fragments of the tiles, but also the half-burned timber, reached the soldiers: the flames spread wide, and the smoke caused a degree of terror even greater than the danger. [12] In consequence, the Romans who were without the city, and were just then making the principal attack, retired from the wall; and those who were within, fearing lest the fire, rising behind them, should put it out of their power to rejoin the rest of the army, began to retreat. Whereupon Quinctius, seeing how matters stood, ordered a general retreat to be sounded. [13] —Thus, being at length recalled from a city which they had nearly taken, they returned to their camp.