Byzantine – Norman wars A number of wars between the Normans and the Byzantine Empire were fought from " c " . 1050 until 1185 when the last Norman invasion of Byzantine territory was defeated . At the end of the conflict , neither the Normans nor the Byzantines could boast much power ; by the mid - 13th century exhaustive fighting with other powers had undermined the rule of both with the Turks conquering Asia Minor from the Byzantines later in the 14th century . The Normans meanwhile had lost Sicily earlier on to the Hohenstaufen who in turn were succeeded by the Angevins and finally the Aragonese . Conquest of Southern Italy ( " c " . 1050 – 1071 ) . The Normans had come from the Duchy of Normandy in West Francia , which in 911 had been granted to the Viking Rollo in the Treaty of Saint - Clair - sur - Epte by the French king Charles the Simple . The Normans and their new land took the name of these " Northmen " . During the time that the Normans had conquered southern Italy , the Byzantine Empire was in a state of internal decay ; the administration of the Empire had been wrecked , the efficient government institutions that provided Basil II with a quarter of a million troops and adequate resources by taxation had collapsed within a period of three decades . Attempts by Isaac I Komnenos and Romanos IV Diogenes to reverse the situation proved unfruitful . The premature death of the former and the undeserving overthrow of the latter led to further collapse as the Normans consolidated their conquest of Sicily and Italy . Reggio Calabria , the capital the of tagma of Calabria , was captured by Robert Guiscard in 1060 . At the time , the Byzantines held a few coastal towns in Apulia , including the capital of the catepanate of Italy , Bari . Otranto was besieged and fell in the October 1068 ; in the same year , the Normans besieged Bari itself and , after defeating the Byzantines in a series of battles in Apulia , and after any attempt of relief had failed , the city surrendered in April 1071 , ending the Byzantine presence in southern Italy . Conquest of the Balkans ( 1081 – 1085 ) . Following their successful conquest of southern Italy , the Normans saw no reason to stop ; Byzantium was decaying further still and looked ripe for conquest . When Alexius I Comnenus ascended to the throne of Byzantium , his early emergency reforms , such as requisitioning Church money - a previously unthinkable move - proved too little to stop the Normans . Led by the formidable Robert Guiscard and his son Bohemund , they took Dyrrhachium and Corfu , and laid siege to Larissa in Thessaly ( see Battle of Dyrrhachium ) . Alexios suffered several defeats before being able to strike back with success . He enhanced this by bribing the German king Henry IV with 360 , 000 gold pieces to attack the Normans in Italy , which forced the Normans to concentrate on their defenses at home in 1083 – 1084 . He also secured the alliance of Henry , Count of Monte Sant ' Angelo , who controlled the Gargano Peninsula and dated his charters by Alexios ' reign . Henry ' s allegiance was to be the last example of Byzantine political control on peninsular Italy . The Norman danger ended for the time being with the death of Robert Guiscard in 1085 combined with a Byzantine victory and crucial Venetian aid allowed the Byzantines to retake the Balkans . Rebellion of Antioch ( 1104 – 1140 ) . Following the First Crusade , a large number of Normans naturally joined in what appeared to be a great expedition into the unknown where land and loot was plentiful . During this time , the Byzantines were able to some extent utilize the aggressive Normans to defeat the Seljuk Turks in numerous battles and many cities fell . However when Antioch fell the Normans refused to hand it over although in time Byzantine domination was established . With the death of John Comnenus the Norman Principality of Antioch rebelled once again , attacking Cyprus and invading Cilicia , which also rebelled . The quick and energetic response of Manuel Comnenus allowed the Byzantines to extract an even more favorable " modus vivendi " with Antioch ( in 1145 being forced to provide Byzantium with a contingent of troops and allow a Byzantine garrison in the city ) . However , the city was given guarantees of protection against Turkic attack and Nur ad - Din Zangi abstained from attacking the northern parts of the Crusader states as a result . Second Norman invasion of the Balkans ( 1147 – 1149 ) . In 1147 the Byzantine empire under Manuel I Comnenus 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 . The death of Roger in February 1154 , who was succeeded by William I , combined with the widespread rebellions against the rule of the new King in Sicily and Apulia , the presence of Apulian refugees at the Byzantian court , and Frederick Barbarossa ' s ( Conrad ' s successor ) failure to deal with the Normans encouraged Manuel to take advantage of the multiple instabilities that existed in the Italian peninsula . He sent Michael Palaiologos and John Doukas , both of whom held the high imperial rank of " sebastos " , with Byzantine troops , 10 Byzantine ships , and large quantities of gold to invade Apulia ( 1155 ) . The two generals were instructed to enlist the support of Frederick Barbarossa , since he was hostile to the Normans of Sicily and was south of the Alps at the time , 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 . Third Norman invasion of the Balkans ( 1185 – 1186 ) . Although the last invasions and last large scale conflict between the two powers lasted less than two years , the third Norman invasions came closer still to taking Constantinople . The incompetent rule of Andronicus Comnenus allowed the Normans to go unchecked towards the Byzantine capital giving Thessalonica a savage sack ( a grim portent of what Constantinople would face in 20 years time ) . The resulting panic , however , allowed Isaac Angelus to take the throne and , after defeating the confident opponent , push the invaders back to Sicily , with the exception of the County palatine of Cephalonia and Zakynthos , the latter remaining in the hands of Norman admiral Margaritus of Brindisi and his successors until 1479 . Aftermath . With the Normans unable to take the Balkans , they turned their attention to European affairs . The Byzantines meanwhile had not possessed the will or the resources for any Italian invasion since the days of Manuel Comnenus . After the third invasion , the survival of the Empire became more important to the Byzantines than a mere province on the other side of the Adriatic Sea . The Norman dynasty was succeeded 1194 by the Hohenstaufen , themselves being replaced in 1266 by the Angevins . The successive Sicilian rulers would eventually continue the Norman policy of domination over post - Byzantine states in the Ionian Sea and Greece , attempting to assert suzerainty over Corfu , finally conquered in 1260 , the County palatine of Cephalonia and Zakynthos , the Despotate of Epirus and other territories .