John III or John IV was the duke of Amalfi briefly in 1073 by right of succession following the death of his father, Sergius III

Sergius III of Amalfi

Sergius III was the duke of Amalfi from 1069, when he succeeded his father John II, until his death. He was first appointed co-regent by his father in 1031...

, in November. John was only an infant when his father died, The Amalfitans, who required a ruler who could defend them, quickly deposed and exiled him. Consequently, given the lack of an adult ruler, Amalfi surrendered to the Normans

Normans

The Normans were the people who gave their name to Normandy, a region in northern France. They were descended from Norse Viking conquerors of the territory and the native population of Frankish and Gallo-Roman stock...

 led by Robert Guiscard

Robert Guiscard

Robert d'Hauteville, known as Guiscard, Duke of Apulia and Calabria, from Latin Viscardus and Old French Viscart, often rendered the Resourceful, the Cunning, the Wily, the Fox, or the Weasel was a Norman adventurer conspicuous in the conquest of southern Italy and Sicily...

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