Siege of Pavia ( 773 – 74 ) The Siege or Battle of Pavia was fought in 773 – 774 in northern Italy , near Ticinum ( modern Pavia ) , and resulted in the victory of the Franks under Charlemagne against the Lombards under king Desiderius . Background . Charlemagne , " rex Francorum " , had succeeded to the throne in 768 jointly with his brother Carloman . At the time there was antagonism between not only the two ruling brothers , but between the king of the Lombards , Desiderius , and the papacy . In 772 , Pope Hadrian I expelled all the Lombard officials from the papal curia . In response , Desiderius invaded papal territory , even taking Otriculum ( modern Otricoli ) , just a day ' s march from Rome . Hadrian called Charlemagne for assistance . Charles had produced an alliance with the Lombards by marrying one of Desiderius ' daughters , Desiderata ; within a year , however , he had changed his mind about the marriage and alliance , and divorced his wife , sending her back to her father . This was taken as an insult by the Lombards . Upon the death of Carloman in 771 , his own wife , Gerberge fled the kingdom with her children for reasons now unclear ( Einhard disingenuously protests that she spurned her husband ' s brother " for no reason at all " ) and sought refuge with Desiderius at Pavia . Desiderius now returned the insult to the Franks by giving her asylum , and protesting that her children be allowed their share of the Kingdom of the Franks . The relationship between Frank and Lombard now broke down completely and the pope took full advantage . His embassy landed at Marseilles and travelled to Thionville , where they delivered this message : 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 . Siege . Charles army was of an unknown number ; he divided it in half , giving command of one half to his uncle , Bernard , son of Charles Martel ; and led it through the Alpine passes , he through that of the Dora Susa near Mont Cenis and Bernard through the Great St Bernard Pass . At the foot of the mountains , Charles ' army met the fortifications of Desiderius , but scouting forces found an alternate route . A cavalcade was sent to attack the defenders from the flank and , with Bernard ' s forces approaching from the east , the Lombards fled to fortified Pavia . The Frankish troops then marched on to begin the siege of Pavia by September . The entire Frankish army was capable of wholly surrounding the Lombard capital . They had brought no siege engines , however . The Lombards too had failed in their preparations : the city was poorly stocked with food and the surrounding countryside was now in the hands of the Franks . Desiderius remained in Pavia , but Adelchis , his son , had left to stronger Verona to guard over the family of Carloman . Charles led a small force to besiege Verona . Adelchis fled in fear to Constantinople and the city and Carloman ' s family were taken . Charles then began to subdue the whole region around Pavia in the early months of 774 . Charles even visited the pope in Rome at Easter . No other Lombard dukes or counts made any attempt at relief and Desiderius made no strong counterattack . 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 . Legacy . After the victory , Charlemagne had himself declared " rex Langobardorum " , and from that time onwards he was to be called King of the Franks " and " Lombards . This was unique in the history of the Germanic kingdoms of the Dark Ages : a ruler taking the title of the conquered . Charles was forging what could truly be called an " empire " . He was also allying himself very closely with the church as its protector . His recognition of temporal papal authority in central Italy laid the foundation for mediaeval Papal power . The decline of the Lombard state had been swift and the changes wrought in Italy by the Frankish conquest were great . Many Franks entered into positions of power and authority in Italy , though many Lombards , on account of their willingness to make peace with Charles , retained their positions . 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 . "