Following Roman rule, Sicily, Corsica and Sardinia were conquered by the Vandals, then by the Ostrogoths, and finally by the Byzantines. At one point, Sardinia grew increasingly autonomous from the Byzantine rule to the point of organizing itself into four sovereign Kingdoms, known as "Judicates", that would last until the Aragonese conquest in the 15th century. Corsica came under the influence of the Kingdom of the Lombards and later under the maritime Republics of Pisa and Genoa. In 687, Sicily became the Byzantine Theme of Sicily; during the course of the Arab–Byzantine wars, Sicily gradually became the Emirate of Sicily (831–1072). Later, a series of conflicts with the Normans would bring about the establishment of the County of Sicily, and eventually the Kingdom of Sicily. The Lombards of Sicily (not to be confused with the "Longobards"), coming from Northern Italy, settled in the central and eastern part of Sicily. After the marriage between the Norman Roger I of Sicily and Adelaide del Vasto, descendant of the Aleramici family, many Northern Italian colonisers (known collectively as "Lombards") left their homeland, in the Aleramici's possessions in Piedmont and Liguria (then known as "Lombardy"), to settle on the island of Sicily.