Kingdom of Sicily
Unlike the north, with its network of vigorously independent urban centers, southern Italy experienced a significant consolidation after its conquest by the Normans. Bands of these invaders arrived in Italy in early 11th century.
Starting c.1045, Robert Guiscard (a Norman adventurer) and his successors expelled the Saracens and Byzantines and established a powerful foothold in Apulia Calabria, Campania, and Sicily. Although the Norman territories remained an anchor of the papacy, papal over lordship became a mere formality in the 12th century, and when Roger II united the southern part of the peninsula with Sicily, he assumed the title of King of Sicily in 1130.
While the Normans were consolidating their power in southern Italy, the papacy and the Holy Roman Empire continued their struggle for dominance in northern and central Italy. In 1077, Pope Gregorius VII humbled Holy Roman Emperor Henry IV at Canossa during the Investiture Controversy. Later, Pope Alexander III successfully supported an alliance of northern cities known as the Lombard League against the efforts of Emperor Frederick I of the Hohenstaufen dynasty to impose imperial authority over them.
Early in the 13th century the Hohenstaufen Frederick II succeeded in uniting the thrones of German and Norman Sicily. Although Pope Inocentius III (r. 1198-1216) opposed the emperor and advanced far-reaching claims of political and religious supremacy, Frederick established one of the wealthiest and most powerful states in Europe, centering on his brilliant court at Palermo, with its great cultural innovations.
The papal-imperial conflict culminated in 1262 with a papal invitation to Charles of Anjou (brother of King Louis IX of France), to conquer Sicily. Charles, the founder of the Amgevin dynasty of Naples, ruled from 1266 as Charles I, king of Naples and Sicily. French rule, which introduced feudalism to the south at a time when it was weakening elsewhere, was highly unpopular, and in 1282 a successful revolt (the Sicilian Vespers) resulted in the separation of Sicily from the mainland.
Peter III of Aragon was made king of Sicily while the former Norman domains on the mainland remained under Amgevin rule as the Kingdom of Naples. However, in the 15th century both kingdoms became Spanish possessions; they were then reunited under the title Kingdom of the Two Sicilies.