The Ghibeline supremacy was short-lived. Their nobles, especially the great house of the Uberti, became unpopular by reason of the exactions which they enforced; they got beaten in a fight with some of the banished Guelfs at no great distance from the city; and before the end of 1250 a meeting of “the good men,” as Villani calls them, or, as we should say, the middle class, limited the power of the Podestà,[16] and appointed a Captain of the People to manage the internal affairs of the city, with a council of twelve Elders. Other important changes were made at the same time, and the new constitution--the third recorded in Florentine history--was known as the “Primo Popolo.” The death of Frederick in the same year still further weakened the Ghibelines. Some of them were banished, and the exiled Guelfs were recalled. Peace, however, seems to have been kept between the parties for some time, and when in 1255 Count Guido Guerra on his own account expelled the Ghibelines from Arezzo, the Florentines restored them, and lent the Aretines money to pay a fine which the Guelf chief had inflicted; “but I know not if they ever got it back,” says Villani. Again the compromise proved unstable. Manfred, Frederick’s natural son, to whom, during the childhood of his young nephew, Conradin, the championship of the Hohenstaufen cause had fallen, was daily increasing in strength. His orders came to the Ghibelines of Florence to crush the popular party; and the latter, being warned in time, drove out all the great Ghibeline families. Two years later these had their revenge. On September 4, 1260, a date much to be remembered in the history of these times, the banished Ghibelines, aided by eight hundred of Manfred’s German horse, seized the opportunity of hostilities between the Florentines and the Sienese to meet their opponents in a pitched battle. This took place on the Arbia, near the fortress of Montaperti, to the east of Siena.[17] The Guelfs were utterly routed, partly, it would seem, through the incompetence of some of the Elders who accompanied the army, and who, civilians though they were, overruled the judgement of the military leaders, and accepted battle under unfavourable conditions; and partly through the treachery of some Ghibelines who, not having been exiled, were serving in the Florentine host. Readers of the _Commedia_ will remember the name of Bocca degli Abati, placed by Dante in the lowest pit of hell.[18]