structural:summarization
Roger II of Sicily

In 1147 Manuel was faced with war by Roger II of Sicily, whose fleet had captured the Byzantine island of Corfu and plundered Thebes and Corinth. However, despite being distracted by a Cuman attack in the Balkans, in 1148 Manuel enlisted the alliance of Conrad III of Germany, and the help of the Venetians, who quickly defeated Roger with their powerful fleet. In 1149, Manuel recovered Corfu and prepared to take the offensive against the Normans, while Roger II sent George of Antioch with a fleet of 40 ships to pillage Constantinople's suburbs. Manuel had already agreed with Conrad on a joint invasion and partition of southern Italy and Sicily. The renewal of the German alliance remained the principal orientation of Manuel's foreign policy for the rest of his reign, despite the gradual divergence of interests between the two empires after Conrad's death.

Roger died in February 1154 and was succeeded by William I, who faced widespread rebellions against his rule in Sicily and Apulia, leading to the presence of Apulian refugees at the Byzantine court. Conrad's successor, Frederick Barbarossa, launched a campaign against the Normans, but his expedition stalled. These developments encouraged Manuel to take advantage of the multiple instabilities on the Italian peninsula. He sent Michael Palaiologos and John Doukas, both of whom held the high imperial rank of sebastos, with Byzantine troops, ten ships and large quantities of gold to invade Apulia in 1155. The two generals were instructed to enlist the support of Frederick, but he declined because his demoralised army longed to get back north of the Alps as soon as possible. Nevertheless, with the help of disaffected local barons, including Count Robert of Loritello, Manuel's expedition achieved astonishingly rapid progress as the whole of southern Italy rose up in rebellion against the Sicilian Crown and the untried William I. There followed a string of spectacular successes as numerous strongholds yielded either to force or the lure of gold.