[4]Charlemagne ascertained the truth of Desiderius' aggressions and the threat he posed to his own Frankish realm and marched his troops towards Italy in the early summer of 773.

In the tenth month of the siege, famine was hitting Pavia hard and Desiderius, realising that he was left on his own, opened the gates to Charles and surrendered on some Tuesday in June.

As Paul K. Davis writes, "The defeat and consequent destruction of the Lombard monarchy rid Rome of its most persistent threat to Papal security, laying the groundwork for the Holy Roman Empire.

"[5] In Pavia, where the memory of the Lombard reasoning and the role of capital of the city characterized the urban identity for centuries,[6] there are some testimonies of the siege, some contemporary, such as the sections of the first walls preserved in via dei Mulini, others, albeit later, very significant, such as the cycle of the stories of Saint Theodore of Pavia frescoed in the right aisle of the church of San Teodoro.

The painting, commissioned in 1514 by the rector of the church Giovanni Luchino Corti to an anonymous Lombard artist,[7] depicts some episodes in the life of the holy bishop of Pavia and in particular during the siege of 773-774, which significantly fails in the pictorial cycle.

Theodore in fact caused the Ticino waters to swell, flooding the Frankish camp and forcing Charlemagne to abandon the siege.

[8] Always linked to the memory of the siege is the small church of Santa Sofia (Torre d'Isola) located on a high terrace of Ticino a few kilometers west of the city, which according to a legend (based on the story handed down by the chronicler Notker the Stammerer) was built by Charlemagne during the siege of Pavia in just one day in order to better attend the divine services.

However, beyond the imaginative narration of the chronicler, a royal residence certainly arose in the church in the ninth century, in which Louis II of Italy[9] and then Charles the Bald stayed first in the year 876.