Carolingian emperors but ignore their rulings. As a result, De facto independence was achieved from Frankish as well as Byzantine authority. The Duchy of Benevento reached its territorial peak under Sicard in the 830s. At his time, the Mezzogiorno was suffering the ravages of the Saracens, against whom Sicard warred constantly. He also warred against his Byzantine neighbours, especially Sorrento, Naples, and Amalfi. It was in a war with Naples that Duke Andrew II first called in Saracen mercenaries. In 839, Sicard was assassinated and a civil war broke out which illustrated the nature of political power in the south. It was still largely in the hands of the land-owning aristocracy, who had the power to choose a prince. In 839, some chose Radelchis I, the treasurer and assassin, and some chose Siconulf of Salerno, who was installed at Salerno. This civil war continued apace for a decade, during which the gastaldates of Benevento took the opportunity to entrench their independence, especially Capua, which sided with Siconulf. In 849, the Emperor Louis II, in one of his first acts as King of Italy, invaded the peninsula and imposed peace between the Lombard factions. He divided the principality into two: one at Benevento, one at Salerno. Thenceforward, the history of the Lombard south is one of declining, competing powers. In the Tyrrhenian Greek cities, the violence raging inland, between them and their fellow Greeks on toe and heel, fostered the circumstances of de facto independence. Naples, in particular, had a history of differences with Byzantium and had in the past sought to make herself dependent on other authorities, often papal. In 801, the Byzantine patrician of Sicily succeeded in creating Anthimus duke. However, Anthimus was unable to control the cities under his rule, Gaeta and Amalfi. Subsequent to Anthimus, the patrician tried to appoint his own candidate without imperial approval. The people rebelled and accepted Stephen III in 821. During Stephen's decade of rule, Naples severed all legal ties to Constantinople and even began minting her own coins. In 840, after a brief flirtation with Frankish servitude, to Lothair I, and a Frankish duke, in the person of Duke Contard, the Neapolitan citizenry elected Sergius I their magister militum. Sergius established a dynasty, the Sergi, that was to rule the duchy for the next three hundred years. In Gaeta, as in Naples, the violent situation inland required new power structures to