Adhemar was the Duke of Spoleto from 998 and Prince of Capua from 1000. Before his death, he lost both domains. He is not mentioned as duke of Spoleto after December 999.

He was the son of Balsamo, a Capuan cleric. He was educated at the court of Otto II

Otto II, Holy Roman Emperor

Otto II , called the Red, was the third ruler of the Saxon or Ottonian dynasty, the son of Otto the Great and Adelaide of Italy.-Early years and co-ruler with Otto I:...

, alongside the future emperor Otto III

Otto III, Holy Roman Emperor

Otto III , a King of Germany, was the fourth ruler of the Saxon or Ottonian dynasty of the Holy Roman Empire. He was elected King in 983 on the death of his father Otto II and was crowned Holy Roman Emperor in 996.-Early reign:...

.

In order to break the power of Hugh the Great

Hugh of Tuscany

Hugh the Great was the Margrave of Tuscany from 961 to his death and Duke of Spoleto and Camerino from 989 to 996. He was the son and successor of Humbert of Tuscany, who was also briefly Duke of Spoleto, and Willa, a daughter of Boniface I of Spoleto...

, margrave of Tuscany, who had become duke of Spoleto, Otto III appointed one Conrad as duke in May 996. In December 998, Otto appointed his childhood companion Adhemar as duke. Otto then took him south and they marched on Capua

Capua

Capua is a city and comune in the province of Caserta, Campania, southern Italy, situated 25 km north of Naples, on the northeastern edge of the Campanian plain. Ancient Capua was situated where Santa Maria Capua Vetere is now...

, where Laidulf

Laidulf of Capua

Laidulf was a son, probably the youngest or second youngest, of Pandulf Ironhead. He probably never expected to inherit much, especially with so many cousins vying for their rightful inheritances. He was the count of Teano...

, the reigning prince, was removed from his position for the assassination of his brother. They then marched on Naples

Naples

Naples is a city in Southern Italy, situated on the country's west coast by the Gulf of Naples. Lying between two notable volcanic regions, Mount Vesuvius and the Phlegraean Fields, it is the capital of the region of Campania and of the province of Naples...

 and took Duke John IV

John IV of Naples

John IV was the mostly absentee duke of Naples from 997 to after 1002. He was the son and successor of Sergius III. John IV originally recognised the suzerainty of the Byzantine Emperor....

 captive to Capua. Laidulf, along with his wife Maria and Gaideris and Lando of Caiazzo, were exiled from the city and Adhemar was left in charge. John of Naples was taken back by Otto to Germany. In March 1000, Adhemar was named prince. By July he was removed by the Capuans, who elected Landulf of Sant'Agata

Landulf VII of Capua

Landulf VII , also numbered Landulf IV or V , called Landolfo di Sant'Agata, was the prince of Capua from 1000 to his death. He was the second son of Landulf III of Benevento, who was only ever a co-ruler. Thus, he was easily removed from the succession on his father's death...

 instead. As prince, however, he did create Atenulf as count of Aquino

Aquino

Aquino is a town and comune in the province of Frosinone, in the Lazio region of Italy, 12 km northwest of Cassino.-History:The ancient Aquinum was a municipium in the time of Cicero, and made a colony by the Triumviri...

, thus inaugurating that dynasty.