Pope Leo III led the traditional procession along Via Flaminia (today Via del Corso) in 799. Two nobles who disliked his allegiance with Charlemagne attacked and wounded the pope. Leo escaped to the kingdom of the Franks, and the following year the king entered Rome with an army. He announced that a trial would be held to determine if Leo should remain pope or if the nobles had had just causes. Naturally, Leo was declared legitimate and the attackers were exiled. Leo crowned Charlemagne the Emperor of Western Rome on December 25, 800.

The connection between Rome and Constantinople was severed for good. This act resulted in a rival empire, which came to encompass the majority of Christian territories in the west after the military triumphs of Charlemagne. 

After the Emperor’s death, it was difficult to find a successor as prestigious and determined as Charlemagne. Political and economic strife ensued. As a result, Rome’s power weakened. At this time, the Arabs had become a major threat throughout Europe. In 846, they approached Rome and sacked St. Peter’s Basilica. Pope Leo IV reacted by building another wall around an area on the bank of the Tiber across from the seven hills of Rome. This territory is called the Leonine City today. It encompasses the Vatican, Borgo and other areas.

During this period, the Church began to attract pilgrims from across Christian lands, and their money came with them. Although Rome had only 30,000 inhabitants, it became a wealthy and prosperous city.  The new class of merchants and businessmen was beginning to replace the old aristocracy. Rome was sacked by the Normans in 1084, and its reconstruction was funded by affluent families like the Pierleonis. Inspired by the cities of Viterbo and Tivoli, Rome began to aspire toward freedom from papal authority and a communal status. The Romans revolted in 1143. The Roman Republic had been reborn, together with the Senate and other republican institutions.