The kingdom of the Lombards endured two centuries, and left ineffaceable marks upon Italy.  A cordon of military cities was drawn round the old Roman centers in Lombardy, Tuscany, and the Duchy of Spoleto.  Pavia rose against Milan, which had been a second Rome, Cividale against Aquileia, Fiesole against Florence, Lucca against Pisa.  The country was divided into Duchies and Marches; military service was exacted from the population, and the laws of the Lombards, asininum jus, quoddam jus quod faciebant reges per se, as the jurists afterwards defined them, were imposed upon the descendants of Roman civilization.  Yet the outlying cities of the sea-coast, as we have already seen, were independent; and Rome remained to be the center of revolutionary ideas, the rallying-point of a policy inimical to Lombard unity.  Not long after their settlement, the princes of the Lombard race took the fatal step of joining the Catholic communion, whereby they strengthened the hands of Rome and excluded themselves from tyrannizing in the last resort over the growing independence of the Papal See.  The causes of their conversion from Arianism to orthodox Latin Christianity are buried in obscurity.  But it is probable that they were driven to this measure by the rebelliousness of their great vassals and the necessity of resting for support upon the indigenous populations they had subjugated.  Rome, profiting by the errors and the weakness of her antagonists, extended her spiritual dominion by enforcing sacraments, ordeals, and appeals to ecclesiastical tribunals, organized her hierarchy under Gregory the Great, and lost no opportunity of enriching and aggrandizing her bishoprics.  In 718 she shook off the yoke of Byzantium by repelling the heresies of Leo the Isaurian; and when this insurrection menaced her with the domestic tyranny of the Lombard Kings, who possessed themselves of Ravenna in 728, she called the Franks to her aid against the now powerful realm.  Stephen II. journeyed in 753 to Gaul, named Pippin Patrician of Rome, and invited him to the conquest of Italy.  In the war that followed, the Franks subdued the Lombards, and Charles the Great was invested with their kingdom and crowned Emperor in 800 by Leo III. at Rome.

The famous compact between Charles the Great and the Pope was in effect a ratification of the existing state of things.  The new Emperor took for himself and converted into a Frankish Kingdom all the provinces that had been wrested from the Lombards.  He relinquished to the Papacy Rome with its patrimony, the portions of Spoleto and Benevento that had already yielded to the See of S. Peter, the southern provinces that owned the nominal ascendency of Byzantium, the islands and the cities of the Exarchate and Pentapolis which formed no part of the Lombard conquest.  By this stipulation no real temporal power was accorded to the Papacy, nor did the new Empire surrender its paramount rights over the peninsula at large.  The Italian