For nearly two centuries, Norman armies challenged Byzantine power from southern Italy to the Balkans. George Theotokis examines the tactics, campaigns and political ambitions that shaped this long struggle between two medieval powers.
By George Theotokis
Writing in the mid-twelfth century, Anna Komnene presented the Franks/Normans through a distinctly Byzantine lens, emphasizing their military prowess while reinforcing long-standing cultural stereotypes. She famously remarked in her Alexiad, “For a Frank on horseback is invincible, and would even make a hole in the walls of Babylon, but directly he gets off his horse, anyone who likes can make sport of him.” Elsewhere, she characterizes the Franks as reckless, greedy, impulsive, and prone to breaking agreements, portraying them as formidable cavalrymen but unreliable allies whose behaviour reflected Byzantine perceptions of western “barbarians.” These descriptions, together with her portraits of Robert Guiscard and Bohemond, reveal more about Byzantine attitudes toward the Normans than about Frankish military culture itself.
Norman battlefield tactics rested on three closely related principles. First, they used the couched lance in battle, whereby the rider tightly braces the lance between the arm and torso in order to channel the horse’s momentum into the penetrative force of the weapon. This technique became closely associated with mounted shock combat in western Europe during the High Middle Ages. Although earlier scholarship placed the development of mounted shock combat and the couched lance between c. 1050 and 1150, more recent studies emphasize that medieval warfare was far more diverse and cannot be explained by a single tactical innovation. Moreover, while the Normans made the massed cavalry charge their principal offensive tactic, the couched lance itself was not a Western invention, having long been employed in Byzantine, Georgian, Iranian, and Muslim military traditions across the eastern Mediterranean and the Caucasus.
Second, their decisive offensive weapon was the massed heavy cavalry charge, delivered by disciplined mounted knights using the couched lance. Rather than relying on individual combat, the Normans sought to concentrate the momentum of an organized cavalry assault to break enemy formations, a tactic that proved highly effective in battles such as Civitate (1053), Dyrrachium (1081), and later engagements in southern Italy. Their success depended not only on the shock effect of the charge but also on exploiting exposed flanks, pursuing broken formations, and maintaining battlefield cohesion through effective leadership and command.
Finally, Norman commanders demonstrated considerable tactical flexibility and an appreciation for combined-arms warfare. Although cavalry remained the decisive arm, infantry and missile troops supported mounted operations by protecting the flanks, fixing enemy formations, and creating opportunities for cavalry to strike at vulnerable points. Campaigns in Italy, Sicily, and the Balkans also reveal an ability to adapt tactics to different operational environments, employing naval blockades, siege warfare, amphibious operations, and manoeuvre when direct assault was impractical. Rather than relying exclusively on cavalry charges, Norman success stemmed from integrating heavy cavalry with infantry, archers, and strategic adaptability, allowing them to overcome a wide variety of opponents across the Mediterranean.
The Normans Arrive in Byzantine Italy
Image by MapMaster / Wikimedia Commons
The first recorded involvement of the Normans in Italy occurred in 1017, when approximately 250 Norman soldiers participated as auxiliaries in a Lombard uprising in northern Apulia. The Byzantine administration, under the command of Catepan Tornikios Kontoleon, responded rapidly to the revolt. The following year, the Normans joined the forces of the Lombard noble Melus, but the rebellion ended in disaster at the Battle of Cannae (1018), where only a handful of Norman combatants reportedly survived. General Basil Boioannes, supported by contingents from the Varangian Guard, restored Byzantine authority and strengthened imperial control over Apulia by constructing and reinforcing key fortifications, including the fortress of Troia in central Apulia. By 1019, Norman warriors were already serving the Byzantine Empire as mercenaries. Throughout the next two decades (1018–1038), they remained relatively small military contingents that frequently shifted their loyalties according to political and financial opportunities, rather than acting as an independent political force.
A more significant phase of Norman participation began during the reign of Emperor Michael IV (1034–1041), when the Byzantine general George Maniakes launched an expedition to recover Sicily in 1038. His multinational army consisted of Greeks, Bulgarians, Vlachs, Varangians, and between three and five hundred Norman mercenaries commanded by William and Drogo Hauteville. Byzantine chroniclers, including John Skylitzes, record imperial victories in the vicinity of Messina and Syracuse, although they provide little detail regarding the Normans’ battlefield contributions. In contrast, Geoffrey Malaterra attributes a decisive counterattack at Messina to the Norman contingent, highlighting the differing interpretations preserved in the medieval sources.
By 1041, roughly five hundred Normans had established themselves at the strategically important fortress of Melfi in Apulia. Fighting alongside Lombard allies, they defeated Byzantine forces commanded by Catepan Michael Doukeianos at the battles of Olivento and Ofanto, compelling the imperial army to retreat. Later that year, they also repelled another Byzantine expedition sent from Sicily, which included members of the Varangian Guard, although contemporary accounts provide few details about the engagement. Despite these successes, the Normans had not yet become the principal architects of the Apulian revolt. Their military role remained largely supportive, and they had yet to emerge as the dominant political and military power in southern Italy.
Following their decisive victory at the Battle of Civitate on 17 June 1053, which firmly established Norman dominance in southern Italy, the next major confrontation between the Normans and Byzantium occurred with the siege of Bari in 1068. As the administrative centre of the Byzantine province of Longobardia, Bari represented the empire’s final stronghold in southern Italy. Robert Guiscard sought to isolate the city by imposing a naval blockade and constructing floating bridges from chained vessels to secure control of the harbour. At the same time, his forces employed siege engines, including stone-throwing machines and a large wooden siege tower, in an effort to breach the city’s formidable defences. Although the defenders appealed to Constantinople for assistance, the city endured a prolonged siege lasting more than two and a half years before eventually falling. Medieval sources provide only limited information about the day-to-day military operations, instead emphasizing the determination and persistence that characterized Guiscard’s campaign.
In May 1081, Robert Guiscard expanded Norman ambitions beyond Italy by leading an expedition across the Adriatic to invade the Byzantine Empire. His first objective was the strategically important port of Dyrrachium, which he placed under blockade before confronting the forces of the recently crowned Emperor Alexios I Komnenos (r. 1081–1118). On the night of 17 October, Alexios devised a coordinated surprise assault on the Norman encampment, intending to attack simultaneously with the support of Serbian and Turkish allies. The plan, however, was discovered before it could be executed, enabling Guiscard to reorganize his troops and prepare an effective defence against the impending Byzantine offensive.
Miniature of the Byzantine Emperor Alexios I Komnenos (r. 1081-1118)
The Byzantine defeat at Dyrrachium resulted largely from failures in battlefield coordination rather than from a lack of determination among the imperial troops. The Varangian Guard advanced ahead of the main army and became isolated, leaving its flanks vulnerable to Norman attack. Alexios failed to order a timely advance by the remainder of his forces, preventing effective support for the elite guard. Although the Varangians initially resisted with considerable determination and received limited reinforcements, they were eventually overwhelmed by repeated Norman cavalry assaults. Their destruction severely damaged Byzantine morale and triggered the collapse of the imperial battle line. Anna Komnene attributes the disaster primarily to the impetuosity of the English members of the Varangian Guard, but the outcome can more convincingly be explained by deficiencies in command, coordination, and the delayed commitment of supporting forces.
The conflict continued during the following years. In the spring of 1082, Bohemond, Robert Guiscard’s son, inflicted another defeat on Alexios near Ioannina and Arta. Having reflected on the failures at Dyrrachium, the emperor attempted to counter Norman cavalry by deploying wagons equipped with projecting spears alongside fields of caltrops to protect his infantry and restrict mounted attacks. The Normans adapted quickly, bypassing these obstacles with a flanking manoeuvre that once again secured victory.
Alexios altered his strategy during the campaign of 1083. Rather than seeking another decisive engagement, he relied on manoeuvre warfare, avoiding direct confrontation while employing ambushes, deception, and feigned retreats against the advancing Normans around Larisa in Thessaly. This more flexible approach proved considerably more successful. Combined with the intervention of the German emperor Henry IV (r. 1084–1105), whose campaign in Italy forced Robert Guiscard to redirect his attention, Byzantine resistance ultimately contributed to the withdrawal of Norman forces from the Balkans in early 1084.
Bohemond’s Balkan Campaign and the Rise of Roger II
Bohemond I of Antioch on a ship – Bibliothèque nationale de France, Département des manuscrits, Français 9084 f.125v
Robert Guiscard’s Balkan expedition of 1081–1084 was driven by several interconnected political and strategic objectives. One important consideration was the creation of territorial lordships for his younger sons—Guido, Robertus Scalio, and Bohemond—which would ease the succession of his designated heir, Roger Borsa (r. 1085–1111). At the same time, military expansion offered opportunities to reward Norman nobles with land and wealth, reducing the likelihood of unrest within southern Italy. Guiscard also sought to eliminate Byzantine influence in the region, particularly because the governors of Dyrrachium had provided refuge and support to rebellious Norman barons. Beyond these political aims, the conquest of key Adriatic ports promised control over important commercial routes, strengthening Norman influence in Mediterranean trade.
Hostilities between the Normans and Byzantium resumed in 1107 when Bohemond of Antioch launched another invasion of the western Balkans. His campaign was closely linked to the unresolved dispute with Emperor Alexios I Komnenos over the Principality of Antioch. Receiving support from Pope Paschal II (r. 1099–1118) and King Philip I of France (r. 1060–1108), Bohemond presented the expedition as a crusading enterprise and laid siege to Dyrrachium. Rather than risking a pitched battle, Alexios adopted a strategy of attrition. Byzantine forces occupied the surrounding mountain passes, restricting Norman movement, while the combined Byzantine-Venetian fleet severed communication and supply routes across the Adriatic. Isolated from reinforcements, the Norman army suffered from shortages of food, outbreaks of disease, and persistent Byzantine attacks. Mounting losses and desertions eventually compelled Bohemond to negotiate. In September 1108 he accepted the Treaty of Diabolis, whose terms largely favoured Byzantium and effectively ended Norman expansion into the Balkans for the time being.
During the following decades, the balance of power in the central Mediterranean changed considerably. From the early 1120s onward, Roger II gradually united the previously fragmented Norman territories of southern Italy and Sicily. By 1130 this process of consolidation culminated in the creation of the Norman Kingdom of Sicily, with Roger crowned king (r. 1130–1154) under the authority of the antipope Anacletus II. The emergence of this powerful kingdom alarmed neighbouring states and altered the strategic calculations of both the Byzantine Empire and the western powers.
Opposition to Roger II quickly developed. Emperor Lothair III (r. 1133–1137), together with Pope Innocent II (r. 1130–1143), Venice, Pisa, and Genoa, formed a coalition aimed at limiting Norman expansion. Their campaign achieved notable successes, including the capture of Bari in 1137, demonstrating that Roger’s authority in southern Italy was not yet unchallenged.
Mosaic of John II Komnenos in the Hagia Sophia, Istanbul.
Recognising the changing geopolitical landscape, Emperor John II Komnenos (r. 1118–1143) increasingly relied on diplomacy alongside military preparations. A renewed alliance with Venice became a cornerstone of his western policy. This rapprochement reflected two growing concerns: the expansion of Hungarian influence in Dalmatia and the consolidation of Roger II’s kingdom across southern Italy. Earlier tensions between Byzantium and Venice had weakened both powers, creating opportunities for their rivals. To restore cooperation, John strengthened relations with Doge Domenico Michiele in 1126 and later confirmed or expanded Venetian commercial privileges at the ports of Crete and Cyprus in 1136 or 1137.
John II’s broader objective was to prevent Roger II from intervening while Byzantine forces campaigned in Syria against the Principality of Antioch during 1137–1138. Nevertheless, the imperial offensive heightened Norman anxieties. Roger II regarded himself as the legitimate heir to the Hauteville possessions in the Levant and viewed Byzantine advances with increasing suspicion. Although a large-scale Norman invasion of the Balkans did not occur during John’s lifetime, the possibility remained a significant concern within Byzantine strategic planning. Diplomatic initiatives, including the marriage of John’s son and future emperor Manuel I to Bertha of Sulzbach in 1142 and the later marriage alliance involving Henry II Jasomirgott and Theodora Komnene, formed part of a broader effort to strengthen Byzantine ties with the Holy Roman Empire in response to Norman ambitions.
Manuel I Komnenos and the Norman-Byzantine Conflict, 1147–1158
Emperor Manuel I Komnenos depicted in a 12th-century manuscript – Vat. Gr. 1851.
The Norman Kingdom of Sicily presented Emperor Manuel I Komnenos (r. 1143–1180) with the most immediate external threat during the early years of his reign. Shortly after Manuel’s accession, Roger II attempted to establish a political alliance through a dynastic marriage in 1143–1144. These negotiations, however, failed to produce an agreement and instead contributed to a rapid deterioration in relations between the two states.
Roger II exploited the strategic circumstances created by the Second Crusade. While Manuel concentrated much of the Byzantine army in Thrace to supervise the passage of the German and French crusading forces in 1147, the Normans launched a large-scale offensive against imperial possessions. During 1147 and the first half of 1148, a powerful Norman fleet seized Corfu with little resistance before conducting extensive raids across the Ionian and Aegean regions. Kephalonia, Methoni, Neapolis in Lakonia, Athens, Chalkis, Thebes, and Corinth all suffered attacks, with the latter four cities holding particular economic importance as centres of Byzantine silk production. These operations inflicted considerable economic damage while exposing weaknesses in the empire’s maritime defences.
Manuel responded by assembling a coalition with Venice and the German emperor Conrad III. Their combined efforts enabled the Byzantines to recover Corfu in the summer of 1149. At the same time, Roger II attempted to divert imperial attention by dispatching a naval expedition toward Constantinople, hoping to force Manuel to abandon the siege. The strategy proved unsuccessful, as the Norman fleet was decisively defeated by the combined Byzantine and Venetian naval forces operating in the Aegean Sea.
Naval warfare in a 13th-century Byzantine manuscript
Modern scholarship has offered differing interpretations of Roger II’s broader objectives. Historians such as Ferdinand Chalandon, Hélène Ahrweiler, Michael Angold, Donald M. Nicol, Charles D. Stanton, and Ioannis Sarantidis argue that the Norman king intended to establish permanent control over Byzantine territories in Greece and the Ionian Islands. Such expansion would have provided the Normans with influence over the Strait of Otranto and the commercial routes linking the Adriatic and eastern Mediterranean, directly challenging both Byzantine and Venetian maritime interests. Graham Loud, however, proposes a more limited interpretation, suggesting that Roger’s campaigns may have been intended primarily to compel the Byzantine emperor to recognise the legitimacy of the Norman Kingdom of Sicily rather than to achieve large-scale territorial conquest.
Roger II’s death in 1154 significantly altered the political environment. His successor, William I (r. 1154–1166), sought unsuccessfully to negotiate a settlement with Manuel I. Military operations nevertheless continued. During the summer of 1154, the Byzantine fleet suffered a serious defeat near Monemvasia, although another imperial naval force achieved a subsequent victory over the Normans later that year, restoring Byzantine control over the Aegean and demonstrating that the empire retained considerable naval strength despite earlier setbacks.
Determined to exploit political instability within the Norman kingdom, Manuel launched an ambitious expedition to southern Italy in the spring of 1155. Byzantine commanders recruited Italian mercenaries and secured the cooperation of local opponents of Norman rule, although attempts to gain the support of Emperor Frederick I Barbarossa proved unsuccessful. Between late 1155 and May 1156, imperial forces occupied or negotiated the submission of numerous towns along the Adriatic coast, including Bari, Taranto, Brindisi, and Otranto. The capture of these ports served not only offensive purposes but also reflected Byzantine efforts to deny the Normans the same strategic bases from which they had launched attacks against the empire during the campaigns of 1147–1148.
The Italian expedition ultimately ended in failure. In May 1156, William I assembled a powerful army that confronted the Byzantines near Brindisi. The decisive Norman victory reversed the gains achieved during the previous year, and by June the empire had lost all of the territory it had recently recovered in southern Italy. One notable engagement during the campaign occurred near Andria in 1155, where a smaller Byzantine-rebel force supported by Cuman and Alan mercenaries faced a larger Norman army. According to the surviving accounts, the Norman commander initially escaped encirclement and withdrew toward Andria, only to discover that the city was unprepared to withstand a siege.
Forced to accept battle, he launched an aggressive cavalry assault that temporarily disrupted the Byzantine formation and nearly captured one of its commanders. The imperial forces eventually regrouped behind a defensive stone barrier and used missile fire to blunt repeated Norman attacks. During the final assault, the Norman count was struck from his horse by a stone and killed, triggering the collapse of Norman resistance and securing a difficult Byzantine victory. Despite this tactical success, the desertion of several imperial allies soon afterwards fatally weakened Manuel’s campaign, contributing to the broader defeat that culminated at Brindisi.
The objectives of Manuel’s Italian policy remain the subject of scholarly debate. The twelfth-century historian John Kinnamos, reflecting official Byzantine ideology, portrays the emperor as seeking the restoration of imperial authority throughout Italy and Sicily. Western contemporary sources generally describe more modest ambitions, limiting Byzantine objectives to Apulia and the region surrounding Ancona. Ioannis Sarantidis has proposed an intermediate interpretation, arguing that Manuel’s principal aim was to establish control over the chain of coastal cities linking Ancona with Apulia. Such a strategy would have secured the principal maritime communications between Venice and the Ionian Sea while strengthening Byzantine influence in the central Mediterranean.
The Final Phase of Norman-Byzantine Relations and the Invasion of 1185
The Kingdom of Sicily upon the death of Roger II of Sicily in 1154. Wikimedia Commons
Following the unsuccessful Italian campaign of 1155–1156, Manuel I continued his efforts to challenge Norman influence in southern Italy. Between 1157 and 1158, Byzantine forces reportedly occupied several cities in Calabria with the assistance of local Norman rebels opposed to William I’s rule. Although these gains demonstrated that resistance within the Norman kingdom persisted, they proved insufficient to alter the broader balance of power.
William I responded decisively by dispatching a naval expedition into the Aegean during the summer of 1157. The Norman fleet defeated the Byzantine navy in the vicinity of Euboea before carrying out raids against several important coastal settlements, including Chalkis and Almyros. Norman forces also launched an attack on the imperial Blachernae Palace in Constantinople, underscoring both their naval capabilities and their willingness to strike at the symbolic centre of Byzantine authority. Continued warfare convinced both rulers that a negotiated settlement offered greater advantages than prolonged conflict. Consequently, Manuel I and William I concluded an agreement of peace and alliance in early 1158, bringing more than a decade of intermittent hostilities to an end.
Relations between the two powers remained comparatively stable during the following years, encouraging renewed diplomatic initiatives. In 1166, Manuel proposed a dynastic marriage between his daughter, Maria Komnene, and the young Norman king William II (r. 1166–1189), hoping that such a union would strengthen political cooperation and perhaps lay the foundation for a closer relationship between the two states. The Norman court, however, viewed the proposal with suspicion, interpreting it as an attempt to extend Byzantine political influence over the kingdom. Negotiations resumed in 1171–1172, but on that occasion Manuel rejected the revised terms, judging them incompatible with imperial interests. As a result, the opportunity for a lasting dynastic alliance was ultimately lost.
The situation changed dramatically after Manuel’s death in 1180. The ensuing succession crisis weakened the empire’s internal cohesion and reduced its capacity to respond effectively to external threats. These circumstances encouraged William II of Sicily to launch a major invasion in 1185. Norman forces rapidly captured Dyrrachium and Corfu before advancing into Macedonia, where Thessalonica fell after offering only limited resistance. Political instability within Constantinople, together with the ineffective leadership of Emperor Andronikos I Komnenos (r. 1183–1185), prevented the Byzantines from organizing a coordinated defence. Encouraged by these successes, the Normans continued their advance toward the imperial capital.
The Byzantine recovery began only after the accession of Isaac II Angelos in 1185. The new emperor entrusted command of the imperial army to Alexios Branas, whose campaign successfully exploited divisions within the invading Norman forces. Branas achieved a decisive victory at Mosynopolis and followed it with another success near the Strymon River, inflicting severe casualties and destroying Norman offensive momentum. The invaders abandoned Thessalonica, withdrew toward Dyrrachium, and eventually evacuated the Balkans altogether. Byzantine forces recovered Dyrrachium during the following spring, effectively ending the final large-scale Norman invasion of the empire.
George Theotokis received his PhD in History from the University of Glasgow (2010), specializing in medieval military history. He has published numerous articles and monographs on the history of warfare in Europe and the Mediterranean in the medieval and early modern periods, including The Art of War in Byzantium (Arc Humanities Press, 2024). He works as an Assistant Professor of European history at Ibn Haldun University in Istanbul.
For nearly two centuries, Norman armies challenged Byzantine power from southern Italy to the Balkans. George Theotokis examines the tactics, campaigns and political ambitions that shaped this long struggle between two medieval powers.
By George Theotokis
Writing in the mid-twelfth century, Anna Komnene presented the Franks/Normans through a distinctly Byzantine lens, emphasizing their military prowess while reinforcing long-standing cultural stereotypes. She famously remarked in her Alexiad, “For a Frank on horseback is invincible, and would even make a hole in the walls of Babylon, but directly he gets off his horse, anyone who likes can make sport of him.” Elsewhere, she characterizes the Franks as reckless, greedy, impulsive, and prone to breaking agreements, portraying them as formidable cavalrymen but unreliable allies whose behaviour reflected Byzantine perceptions of western “barbarians.” These descriptions, together with her portraits of Robert Guiscard and Bohemond, reveal more about Byzantine attitudes toward the Normans than about Frankish military culture itself.
Norman battlefield tactics rested on three closely related principles. First, they used the couched lance in battle, whereby the rider tightly braces the lance between the arm and torso in order to channel the horse’s momentum into the penetrative force of the weapon. This technique became closely associated with mounted shock combat in western Europe during the High Middle Ages. Although earlier scholarship placed the development of mounted shock combat and the couched lance between c. 1050 and 1150, more recent studies emphasize that medieval warfare was far more diverse and cannot be explained by a single tactical innovation. Moreover, while the Normans made the massed cavalry charge their principal offensive tactic, the couched lance itself was not a Western invention, having long been employed in Byzantine, Georgian, Iranian, and Muslim military traditions across the eastern Mediterranean and the Caucasus.
Second, their decisive offensive weapon was the massed heavy cavalry charge, delivered by disciplined mounted knights using the couched lance. Rather than relying on individual combat, the Normans sought to concentrate the momentum of an organized cavalry assault to break enemy formations, a tactic that proved highly effective in battles such as Civitate (1053), Dyrrachium (1081), and later engagements in southern Italy. Their success depended not only on the shock effect of the charge but also on exploiting exposed flanks, pursuing broken formations, and maintaining battlefield cohesion through effective leadership and command.
Finally, Norman commanders demonstrated considerable tactical flexibility and an appreciation for combined-arms warfare. Although cavalry remained the decisive arm, infantry and missile troops supported mounted operations by protecting the flanks, fixing enemy formations, and creating opportunities for cavalry to strike at vulnerable points. Campaigns in Italy, Sicily, and the Balkans also reveal an ability to adapt tactics to different operational environments, employing naval blockades, siege warfare, amphibious operations, and manoeuvre when direct assault was impractical. Rather than relying exclusively on cavalry charges, Norman success stemmed from integrating heavy cavalry with infantry, archers, and strategic adaptability, allowing them to overcome a wide variety of opponents across the Mediterranean.
The Normans Arrive in Byzantine Italy
The first recorded involvement of the Normans in Italy occurred in 1017, when approximately 250 Norman soldiers participated as auxiliaries in a Lombard uprising in northern Apulia. The Byzantine administration, under the command of Catepan Tornikios Kontoleon, responded rapidly to the revolt. The following year, the Normans joined the forces of the Lombard noble Melus, but the rebellion ended in disaster at the Battle of Cannae (1018), where only a handful of Norman combatants reportedly survived. General Basil Boioannes, supported by contingents from the Varangian Guard, restored Byzantine authority and strengthened imperial control over Apulia by constructing and reinforcing key fortifications, including the fortress of Troia in central Apulia. By 1019, Norman warriors were already serving the Byzantine Empire as mercenaries. Throughout the next two decades (1018–1038), they remained relatively small military contingents that frequently shifted their loyalties according to political and financial opportunities, rather than acting as an independent political force.
A more significant phase of Norman participation began during the reign of Emperor Michael IV (1034–1041), when the Byzantine general George Maniakes launched an expedition to recover Sicily in 1038. His multinational army consisted of Greeks, Bulgarians, Vlachs, Varangians, and between three and five hundred Norman mercenaries commanded by William and Drogo Hauteville. Byzantine chroniclers, including John Skylitzes, record imperial victories in the vicinity of Messina and Syracuse, although they provide little detail regarding the Normans’ battlefield contributions. In contrast, Geoffrey Malaterra attributes a decisive counterattack at Messina to the Norman contingent, highlighting the differing interpretations preserved in the medieval sources.
By 1041, roughly five hundred Normans had established themselves at the strategically important fortress of Melfi in Apulia. Fighting alongside Lombard allies, they defeated Byzantine forces commanded by Catepan Michael Doukeianos at the battles of Olivento and Ofanto, compelling the imperial army to retreat. Later that year, they also repelled another Byzantine expedition sent from Sicily, which included members of the Varangian Guard, although contemporary accounts provide few details about the engagement. Despite these successes, the Normans had not yet become the principal architects of the Apulian revolt. Their military role remained largely supportive, and they had yet to emerge as the dominant political and military power in southern Italy.
Following their decisive victory at the Battle of Civitate on 17 June 1053, which firmly established Norman dominance in southern Italy, the next major confrontation between the Normans and Byzantium occurred with the siege of Bari in 1068. As the administrative centre of the Byzantine province of Longobardia, Bari represented the empire’s final stronghold in southern Italy. Robert Guiscard sought to isolate the city by imposing a naval blockade and constructing floating bridges from chained vessels to secure control of the harbour. At the same time, his forces employed siege engines, including stone-throwing machines and a large wooden siege tower, in an effort to breach the city’s formidable defences. Although the defenders appealed to Constantinople for assistance, the city endured a prolonged siege lasting more than two and a half years before eventually falling. Medieval sources provide only limited information about the day-to-day military operations, instead emphasizing the determination and persistence that characterized Guiscard’s campaign.
In May 1081, Robert Guiscard expanded Norman ambitions beyond Italy by leading an expedition across the Adriatic to invade the Byzantine Empire. His first objective was the strategically important port of Dyrrachium, which he placed under blockade before confronting the forces of the recently crowned Emperor Alexios I Komnenos (r. 1081–1118). On the night of 17 October, Alexios devised a coordinated surprise assault on the Norman encampment, intending to attack simultaneously with the support of Serbian and Turkish allies. The plan, however, was discovered before it could be executed, enabling Guiscard to reorganize his troops and prepare an effective defence against the impending Byzantine offensive.
The Byzantine defeat at Dyrrachium resulted largely from failures in battlefield coordination rather than from a lack of determination among the imperial troops. The Varangian Guard advanced ahead of the main army and became isolated, leaving its flanks vulnerable to Norman attack. Alexios failed to order a timely advance by the remainder of his forces, preventing effective support for the elite guard. Although the Varangians initially resisted with considerable determination and received limited reinforcements, they were eventually overwhelmed by repeated Norman cavalry assaults. Their destruction severely damaged Byzantine morale and triggered the collapse of the imperial battle line. Anna Komnene attributes the disaster primarily to the impetuosity of the English members of the Varangian Guard, but the outcome can more convincingly be explained by deficiencies in command, coordination, and the delayed commitment of supporting forces.
The conflict continued during the following years. In the spring of 1082, Bohemond, Robert Guiscard’s son, inflicted another defeat on Alexios near Ioannina and Arta. Having reflected on the failures at Dyrrachium, the emperor attempted to counter Norman cavalry by deploying wagons equipped with projecting spears alongside fields of caltrops to protect his infantry and restrict mounted attacks. The Normans adapted quickly, bypassing these obstacles with a flanking manoeuvre that once again secured victory.
Alexios altered his strategy during the campaign of 1083. Rather than seeking another decisive engagement, he relied on manoeuvre warfare, avoiding direct confrontation while employing ambushes, deception, and feigned retreats against the advancing Normans around Larisa in Thessaly. This more flexible approach proved considerably more successful. Combined with the intervention of the German emperor Henry IV (r. 1084–1105), whose campaign in Italy forced Robert Guiscard to redirect his attention, Byzantine resistance ultimately contributed to the withdrawal of Norman forces from the Balkans in early 1084.
Bohemond’s Balkan Campaign and the Rise of Roger II
Robert Guiscard’s Balkan expedition of 1081–1084 was driven by several interconnected political and strategic objectives. One important consideration was the creation of territorial lordships for his younger sons—Guido, Robertus Scalio, and Bohemond—which would ease the succession of his designated heir, Roger Borsa (r. 1085–1111). At the same time, military expansion offered opportunities to reward Norman nobles with land and wealth, reducing the likelihood of unrest within southern Italy. Guiscard also sought to eliminate Byzantine influence in the region, particularly because the governors of Dyrrachium had provided refuge and support to rebellious Norman barons. Beyond these political aims, the conquest of key Adriatic ports promised control over important commercial routes, strengthening Norman influence in Mediterranean trade.
Hostilities between the Normans and Byzantium resumed in 1107 when Bohemond of Antioch launched another invasion of the western Balkans. His campaign was closely linked to the unresolved dispute with Emperor Alexios I Komnenos over the Principality of Antioch. Receiving support from Pope Paschal II (r. 1099–1118) and King Philip I of France (r. 1060–1108), Bohemond presented the expedition as a crusading enterprise and laid siege to Dyrrachium. Rather than risking a pitched battle, Alexios adopted a strategy of attrition. Byzantine forces occupied the surrounding mountain passes, restricting Norman movement, while the combined Byzantine-Venetian fleet severed communication and supply routes across the Adriatic. Isolated from reinforcements, the Norman army suffered from shortages of food, outbreaks of disease, and persistent Byzantine attacks. Mounting losses and desertions eventually compelled Bohemond to negotiate. In September 1108 he accepted the Treaty of Diabolis, whose terms largely favoured Byzantium and effectively ended Norman expansion into the Balkans for the time being.
During the following decades, the balance of power in the central Mediterranean changed considerably. From the early 1120s onward, Roger II gradually united the previously fragmented Norman territories of southern Italy and Sicily. By 1130 this process of consolidation culminated in the creation of the Norman Kingdom of Sicily, with Roger crowned king (r. 1130–1154) under the authority of the antipope Anacletus II. The emergence of this powerful kingdom alarmed neighbouring states and altered the strategic calculations of both the Byzantine Empire and the western powers.
Opposition to Roger II quickly developed. Emperor Lothair III (r. 1133–1137), together with Pope Innocent II (r. 1130–1143), Venice, Pisa, and Genoa, formed a coalition aimed at limiting Norman expansion. Their campaign achieved notable successes, including the capture of Bari in 1137, demonstrating that Roger’s authority in southern Italy was not yet unchallenged.
Recognising the changing geopolitical landscape, Emperor John II Komnenos (r. 1118–1143) increasingly relied on diplomacy alongside military preparations. A renewed alliance with Venice became a cornerstone of his western policy. This rapprochement reflected two growing concerns: the expansion of Hungarian influence in Dalmatia and the consolidation of Roger II’s kingdom across southern Italy. Earlier tensions between Byzantium and Venice had weakened both powers, creating opportunities for their rivals. To restore cooperation, John strengthened relations with Doge Domenico Michiele in 1126 and later confirmed or expanded Venetian commercial privileges at the ports of Crete and Cyprus in 1136 or 1137.
John II’s broader objective was to prevent Roger II from intervening while Byzantine forces campaigned in Syria against the Principality of Antioch during 1137–1138. Nevertheless, the imperial offensive heightened Norman anxieties. Roger II regarded himself as the legitimate heir to the Hauteville possessions in the Levant and viewed Byzantine advances with increasing suspicion. Although a large-scale Norman invasion of the Balkans did not occur during John’s lifetime, the possibility remained a significant concern within Byzantine strategic planning. Diplomatic initiatives, including the marriage of John’s son and future emperor Manuel I to Bertha of Sulzbach in 1142 and the later marriage alliance involving Henry II Jasomirgott and Theodora Komnene, formed part of a broader effort to strengthen Byzantine ties with the Holy Roman Empire in response to Norman ambitions.
Manuel I Komnenos and the Norman-Byzantine Conflict, 1147–1158
The Norman Kingdom of Sicily presented Emperor Manuel I Komnenos (r. 1143–1180) with the most immediate external threat during the early years of his reign. Shortly after Manuel’s accession, Roger II attempted to establish a political alliance through a dynastic marriage in 1143–1144. These negotiations, however, failed to produce an agreement and instead contributed to a rapid deterioration in relations between the two states.
Roger II exploited the strategic circumstances created by the Second Crusade. While Manuel concentrated much of the Byzantine army in Thrace to supervise the passage of the German and French crusading forces in 1147, the Normans launched a large-scale offensive against imperial possessions. During 1147 and the first half of 1148, a powerful Norman fleet seized Corfu with little resistance before conducting extensive raids across the Ionian and Aegean regions. Kephalonia, Methoni, Neapolis in Lakonia, Athens, Chalkis, Thebes, and Corinth all suffered attacks, with the latter four cities holding particular economic importance as centres of Byzantine silk production. These operations inflicted considerable economic damage while exposing weaknesses in the empire’s maritime defences.
Manuel responded by assembling a coalition with Venice and the German emperor Conrad III. Their combined efforts enabled the Byzantines to recover Corfu in the summer of 1149. At the same time, Roger II attempted to divert imperial attention by dispatching a naval expedition toward Constantinople, hoping to force Manuel to abandon the siege. The strategy proved unsuccessful, as the Norman fleet was decisively defeated by the combined Byzantine and Venetian naval forces operating in the Aegean Sea.
Modern scholarship has offered differing interpretations of Roger II’s broader objectives. Historians such as Ferdinand Chalandon, Hélène Ahrweiler, Michael Angold, Donald M. Nicol, Charles D. Stanton, and Ioannis Sarantidis argue that the Norman king intended to establish permanent control over Byzantine territories in Greece and the Ionian Islands. Such expansion would have provided the Normans with influence over the Strait of Otranto and the commercial routes linking the Adriatic and eastern Mediterranean, directly challenging both Byzantine and Venetian maritime interests. Graham Loud, however, proposes a more limited interpretation, suggesting that Roger’s campaigns may have been intended primarily to compel the Byzantine emperor to recognise the legitimacy of the Norman Kingdom of Sicily rather than to achieve large-scale territorial conquest.
Roger II’s death in 1154 significantly altered the political environment. His successor, William I (r. 1154–1166), sought unsuccessfully to negotiate a settlement with Manuel I. Military operations nevertheless continued. During the summer of 1154, the Byzantine fleet suffered a serious defeat near Monemvasia, although another imperial naval force achieved a subsequent victory over the Normans later that year, restoring Byzantine control over the Aegean and demonstrating that the empire retained considerable naval strength despite earlier setbacks.
Determined to exploit political instability within the Norman kingdom, Manuel launched an ambitious expedition to southern Italy in the spring of 1155. Byzantine commanders recruited Italian mercenaries and secured the cooperation of local opponents of Norman rule, although attempts to gain the support of Emperor Frederick I Barbarossa proved unsuccessful. Between late 1155 and May 1156, imperial forces occupied or negotiated the submission of numerous towns along the Adriatic coast, including Bari, Taranto, Brindisi, and Otranto. The capture of these ports served not only offensive purposes but also reflected Byzantine efforts to deny the Normans the same strategic bases from which they had launched attacks against the empire during the campaigns of 1147–1148.
The Italian expedition ultimately ended in failure. In May 1156, William I assembled a powerful army that confronted the Byzantines near Brindisi. The decisive Norman victory reversed the gains achieved during the previous year, and by June the empire had lost all of the territory it had recently recovered in southern Italy. One notable engagement during the campaign occurred near Andria in 1155, where a smaller Byzantine-rebel force supported by Cuman and Alan mercenaries faced a larger Norman army. According to the surviving accounts, the Norman commander initially escaped encirclement and withdrew toward Andria, only to discover that the city was unprepared to withstand a siege.
Forced to accept battle, he launched an aggressive cavalry assault that temporarily disrupted the Byzantine formation and nearly captured one of its commanders. The imperial forces eventually regrouped behind a defensive stone barrier and used missile fire to blunt repeated Norman attacks. During the final assault, the Norman count was struck from his horse by a stone and killed, triggering the collapse of Norman resistance and securing a difficult Byzantine victory. Despite this tactical success, the desertion of several imperial allies soon afterwards fatally weakened Manuel’s campaign, contributing to the broader defeat that culminated at Brindisi.
The objectives of Manuel’s Italian policy remain the subject of scholarly debate. The twelfth-century historian John Kinnamos, reflecting official Byzantine ideology, portrays the emperor as seeking the restoration of imperial authority throughout Italy and Sicily. Western contemporary sources generally describe more modest ambitions, limiting Byzantine objectives to Apulia and the region surrounding Ancona. Ioannis Sarantidis has proposed an intermediate interpretation, arguing that Manuel’s principal aim was to establish control over the chain of coastal cities linking Ancona with Apulia. Such a strategy would have secured the principal maritime communications between Venice and the Ionian Sea while strengthening Byzantine influence in the central Mediterranean.
The Final Phase of Norman-Byzantine Relations and the Invasion of 1185
Following the unsuccessful Italian campaign of 1155–1156, Manuel I continued his efforts to challenge Norman influence in southern Italy. Between 1157 and 1158, Byzantine forces reportedly occupied several cities in Calabria with the assistance of local Norman rebels opposed to William I’s rule. Although these gains demonstrated that resistance within the Norman kingdom persisted, they proved insufficient to alter the broader balance of power.
William I responded decisively by dispatching a naval expedition into the Aegean during the summer of 1157. The Norman fleet defeated the Byzantine navy in the vicinity of Euboea before carrying out raids against several important coastal settlements, including Chalkis and Almyros. Norman forces also launched an attack on the imperial Blachernae Palace in Constantinople, underscoring both their naval capabilities and their willingness to strike at the symbolic centre of Byzantine authority. Continued warfare convinced both rulers that a negotiated settlement offered greater advantages than prolonged conflict. Consequently, Manuel I and William I concluded an agreement of peace and alliance in early 1158, bringing more than a decade of intermittent hostilities to an end.
Relations between the two powers remained comparatively stable during the following years, encouraging renewed diplomatic initiatives. In 1166, Manuel proposed a dynastic marriage between his daughter, Maria Komnene, and the young Norman king William II (r. 1166–1189), hoping that such a union would strengthen political cooperation and perhaps lay the foundation for a closer relationship between the two states. The Norman court, however, viewed the proposal with suspicion, interpreting it as an attempt to extend Byzantine political influence over the kingdom. Negotiations resumed in 1171–1172, but on that occasion Manuel rejected the revised terms, judging them incompatible with imperial interests. As a result, the opportunity for a lasting dynastic alliance was ultimately lost.
The situation changed dramatically after Manuel’s death in 1180. The ensuing succession crisis weakened the empire’s internal cohesion and reduced its capacity to respond effectively to external threats. These circumstances encouraged William II of Sicily to launch a major invasion in 1185. Norman forces rapidly captured Dyrrachium and Corfu before advancing into Macedonia, where Thessalonica fell after offering only limited resistance. Political instability within Constantinople, together with the ineffective leadership of Emperor Andronikos I Komnenos (r. 1183–1185), prevented the Byzantines from organizing a coordinated defence. Encouraged by these successes, the Normans continued their advance toward the imperial capital.
The Byzantine recovery began only after the accession of Isaac II Angelos in 1185. The new emperor entrusted command of the imperial army to Alexios Branas, whose campaign successfully exploited divisions within the invading Norman forces. Branas achieved a decisive victory at Mosynopolis and followed it with another success near the Strymon River, inflicting severe casualties and destroying Norman offensive momentum. The invaders abandoned Thessalonica, withdrew toward Dyrrachium, and eventually evacuated the Balkans altogether. Byzantine forces recovered Dyrrachium during the following spring, effectively ending the final large-scale Norman invasion of the empire.
George Theotokis received his PhD in History from the University of Glasgow (2010), specializing in medieval military history. He has published numerous articles and monographs on the history of warfare in Europe and the Mediterranean in the medieval and early modern periods, including The Art of War in Byzantium (Arc Humanities Press, 2024). He works as an Assistant Professor of European history at Ibn Haldun University in Istanbul.
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Top Image: BNF MS Français 755 fol. 91v
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