John I was the duke of Naples from September 711 to his death, probably in 719. The main source for his reign is the Chronicon ducum et principum Beneventi, Salerni, et Capuae et ducum Neapolis.

In 716, while a pestilence swept through Naples, Romuald II of Benevento

Romuald II of Benevento

Romuald II the Younger was the son of Gisulf I and Winiperga. He succeeded as duke of Benevento on the death of his father, which is dated variously as 698, 706, or 707. According to Paul the Deacon, Gisulf reigned 17 years, which would imply his death in 698, but Paul also mentions acts which...

 occupied the castle of Cumae

Cumae

Cumae is an ancient Greek settlement lying to the northwest of Naples in the Italian region of Campania. Cumae was the first Greek colony on the mainland of Italy , and the seat of the Cumaean Sibyl...

. Immediately, Pope Gregory II

Pope Gregory II

Pope Saint Gregory II was pope from May 19, 715 to his death on February 11, 731, succeeding Pope Constantine. Having, it is said, bought off the Lombards for thirty pounds of gold, Charles Martel having refused his call for aid, he used the tranquillity thus obtained for vigorous missionary...

 ordered him to return it and offered compensation if he would. He did not and John led an army against him in 717. As promised, the pope himself contributed 70 pounds of gold to the undertaking.

Sources

• Caravale, Mario (ed). Dizionario Biografico degli Italiani: LV Ginammi – Giovanni da Crema. Rome
  Rome
  Rome is the capital of Italy and the country's largest and most populated city and comune, with over 2.7 million residents in . The city is located in the central-western portion of the Italian Peninsula, on the Tiber River within the Lazio region of Italy.Rome's history spans two and a half...
  
  , 2000.