Adalgis was the son of Desiderius

Desiderius

Desiderius was the last king of the Lombard Kingdom of northern Italy...

 and the prince of the Langobards or Lombardia in Italy

Italy

Italy , officially the Italian Republic languages]] under the European Charter for Regional or Minority Languages. In each of these, Italy's official name is as follows:;;;;;;;;), is a unitary parliamentary republic in South-Central Europe. To the north it borders France, Switzerland, Austria and...

. After his father was defeated by Charlemagne

Charlemagne

Charlemagne was King of the Franks from 768 and Emperor of the Romans from 800 to his death in 814. He expanded the Frankish kingdom into an empire that incorporated much of Western and Central Europe. During his reign, he conquered Italy and was crowned by Pope Leo III on 25 December 800...

 in Pavia

Pavia

Pavia , the ancient Ticinum, is a town and comune of south-western Lombardy, northern Italy, 35 km south of Milan on the lower Ticino river near its confluence with the Po. It is the capital of the province of Pavia. It has a population of c. 71,000...

 in 774, Adalgis took refuge in Byzantium

Byzantium

Byzantium was an ancient Greek city, founded by Greek colonists from Megara in 667 BC and named after their king Byzas . The name Byzantium is a Latinization of the original name Byzantion...

. He hoped to recapture Lombardia with the aid of Empress Irene

Irene (empress)

Irene Sarantapechaina , known as Irene of Athens or Irene the Athenian was a Byzantine empress regnant from 797 to 802, having previously been empress consort from 775 to 780, and empress dowager and regent from 780 to 797. It is often claimed she called herself "basileus" , 'emperor'...

, but when finally given a chance in 787, he was defeated by a coalition consisting of the Franks

Franks

The Franks were a confederation of Germanic tribes first attested in the third century AD as living north and east of the Lower Rhine River. From the third to fifth centuries some Franks raided Roman territory while other Franks joined the Roman troops in Gaul. Only the Salian Franks formed a...

 and the new prince of Benevento, Grimoald III

Grimoald III of Benevento

Grimoald III was the Lombard Prince of Benevento from 788 until his own death. He was the second son of Arechis II and Adelperga. In 787, he and his elder brother Romoald were sent as hostages to Charlemagne who had descended the Italian peninsula as far as Salerno to receive the submission of...

, a vassal loyal to Charlemagne. Adalgis fled to Constantinople

Constantinople

Constantinople was the capital of the Roman, Eastern Roman, Byzantine, Latin, and Ottoman Empires. Throughout most of the Middle Ages, Constantinople was Europe's largest and wealthiest city.-Names:...

, where he died in 788.