The Count of Arras, with some 400 horse and foot, advancing along the Biena, moved round Monteselvoli to fall upon the Florentine left flank; while the rest of the army left their hill, crossed the Arbia and approached the enemies' position--the Florentines in the valley hastening up their own side of Monteselvoli to join the main body. The German heavy cavalry commenced the assault, dashing like dragons into the ranks of the men of Prato, Arezzo and Lucca, horse and men falling in heaps before their terrible lances. The Count Giordano led his _tedeschi_ straight for the centre of the Guelfic army, where the "martinella" rang continuously over the Carroccio of Florence, round which the flower of the burgher army stood. The Count Aldobrandino with his cavalry and the eager Sienese followed up the German onslaught; but the resistance was long and stubborn. At last Bocca degli Abati, the traitor in the troop of Florentine nobles, _hostis e cive factus_ as Leonardo Bruni puts it, struck Jacopo Pazzi with his sword on the arm that upheld one of the standards of the Republic; a portion of the cavalry went over to the enemy; the rest, seeing themselves betrayed, took to flight. Simultaneously the Count of Arras with the reserve, shouting "San Giorgio! San Giorgio!" burst furiously upon the Florentine flank. Then came, in Dante's immortal phrase, "the havoc and the great slaughter that dyed the Arbia red." The Sienese, writes the chronicler Niccolò di Giovanni Ventura, "seemed like unchained lions rushing upon their foes; little did it avail these to call on San Zanobi or Santa Liperata for aid, for they made a greater slaughter of them than do the butchers of their beasts on Good Friday." The infantry were driven from their position down into the valley, only to be ruthlessly massacred. A band of Florentine burghers--the flower of the Primo Popolo--stood to the end in heroic desperation round the Carroccio and the standards, and fell in their places, resisting to the last, embracing and kissing the blood-stained wood of the car as they died. A number of the fugitives took refuge in the little castle of Montaperto and held out there till later in the day, when it was stormed and they were all put to the sword. It was not until evening had come that the Count Giordano and the Gonfalonieri of the Sienese bade that quarter should be given and prisoners accepted. The number of the slain Guelfs probably lies somewhere between 10,000, which is the Sienese estimate, and the 2500 given by Villani. The Carroccio had been taken; the _popolo vecchio_ of Florence was "broken and annihilated," in Villani's terribly expressive phrase; every house in Florence had lost members, and the allied cities suffered only slightly less. Twelve thousand prisoners are said to have been taken.[7] [Illustration: _Lombardi, Siena_ ON THE BATTLEFIELD OF MONTAPERTI]