They were of the Aryan religion. The conquest was violent. After the occupation, the country was divided into many little states, but the Longobards did not succeed in conquering those occupied by the Byzantines. Pavia becomes the capital of the Longobard reign. Their economy was based on agriculture and breeding: the cities decayed, the territory became rich of small fortified settlements, some with enclosure walls of elliptical form, others constituted only by a watchtower, from which the invaders exercised control over the Italian population. In the year 584 Autari, the elect king of the Longobards; years 591-616, Reign of Agilulfo. In 603, Gregorio Magno I (Pope, 590–604) concluded the peace between the Longobards and Byzantines and so started the process of conversion to the Catholicism of the Longobard people. 636–652 Reign of Rotari. In the 643 promulgation of the 'Edict of Rotari', first coding for the barbaric right. 712–744 Reign of Liutprando.
In the first half of the 8th century, the Longobards tried to take advantage of the conflicts between the Church and the Roman aristocracy, who made all of them want to replace the Byzantine: the Esarca was the victim of a murder, and between 733 and 742, Liutprando occupied the Esarcato. 749 Astolfo, the new king of the Longobards, occupies Ravenna and Pentapoli (750–751) and attacks the territories of the Church. But this last one effectively opposed great resistance to the Longobard expansion, and the invaders were forced to donate to the church the important castle of Sutri (729), which will constitute the first nucleus of the Territory of S. Pietro. In 754, called for help from Pope Stefano II (753), the king of the French, Pipino il Breve, comes down in Italy and forces Astolfo, with the peace of Pavia, to give back to the Pope the lands removed to the Byzantine. But in 756, Astolfo resumes his attacks and besieges Rome.
Pipino il Breve comes back down to Italy, defeats Astolfo again, and, according to the Treaty of Pavia, obligates the Longobards to renounce at the Esarcato and at Pentapoli, which were both turned over to the Pope (donation of Pipino). The State of the Church extends itself now from the Duchy of Rome to the Marches and the Romagna. 756-774 reign of Desiderio, who in 772 invades one more time the state of the church. 774 last coming in Italy of the French, calls from Pope Adrian and guided by Carlo Magno, against the Longobards. Desiderio was imprisoned, and Carlo became king of the French and Longobards. In the year 800, Carlo Magno becomes Emperor of Rome, marking the birth of the Sacred Roman Empire.