Medieval Roman Empire: 5 Battles That (Un)Made the Byzantine Empire

Following the disaster at Yarmuk in 636 CE, the Byzantine Empire – also known as the Eastern Roman Empire – lost much of its territory to the Arab invaders. By the early 8th century, the wealthy provinces of Syria, Palestine, Egypt, and North Africa were gone for good. With the imperial armies in full retreat, the Arabs moved into Anatolia, the Empire’s heartland. The capital of Constantinople went through two sieges but was saved by its impregnable walls. In the West, the Danubian frontier collapsed, allowing the Bulgars to carve their kingdom in the Balkans. Yet, Byzantium did not fall. Instead, it bounced back and moved to the offensive during the 9th and 10th centuries, doubling its size.

The militarization of the imperial administration, reorganization of the military, and masterful diplomacy created a powerful medieval state. However, for each enemy defeated, a new one would appear – Seljuks, Normans, Venice, Ottoman Turks… The internal struggles and civil wars further weakened the Empire’s military capabilities and undermined its defenses. After one last revival in the 12th century, the Byzantine Empire started its decline. Two centuries later, the Empire was only a shadow of its former self, consisting of the capital and a small area in Greece and Asia Minor. Finally, in 1453, Constantinople fell to the new rising power – the Ottomans – ending two millennia of Roman history. Here is a list of five pivotal battles that (un) made this great Empire.

Since the beginning of Arab expansion, the Byzantine Empire became its main target. At first, it looked like the forces of Islam would prevail. The Caliphate had beaten one imperial army after another, taking all of the Empire’s eastern provinces. The ancient cities and major Mediterranean centers – Antioch, Jerusalem, Alexandria, Carthage – were gone for good. It did not help that the Byzantine defenses were hampered by internal struggles within the Empire. The situation was so dire that the Arabs besieged Constantinople twice, in 673 and 717-718.

Yet, the impregnable walls, and the inventions like the famed Greek Fire, saved Byzantium from an untimely end. The hostile incursions in Anatolia continued in the 720s, and the intensity of raids increased during the next decade. Then, in 740, the Caliph Hisham ibn Abd al-Malik launched the major invasion. The Muslim force, 90,000 strong (the number probably exaggerated by the historians), entered Anatolia intending to take major urban and military centers. Ten thousand men raided the western coastlands, the recruiting base of the imperial navy, while the main force, 60 000 strong, advanced on Cappadocia. Finally, the third army marched toward the fort of Akroinon, the lynchpin of Byzantine defenses in the region.

Unbeknownst to the hostiles, the imperial army was aware of their movements. The emperor Leo III the Isaurian and his son, future emperor Constantine V, personally led the forces. Details of battle are sketchy, but it appears that the imperial army outmaneuvered the enemy and scored a crushing victory. Both Arab commanders lost their lives, along with 13,200 soldiers.

Although the enemy devastated the area, the remaining two armies failed to take any significant fort or town. Akroinon was a major success for the Byzantines, as it was the first victory where they overcame the Arab troops in pitched battle. In addition, the success convinced the emperor to continue enforcing the policy of iconoclasm, which resulted in the widespread destruction of religious images and the clash with the Pope. The emperor and his successors believed that the worship of icons angered God and brought the Empire to the brink of destruction.

The emperor could have been right, as the Battle of Akroinon was a turning point leading to reduced Arab pressure on the Empire. It also contributed to the weakening of the Umayyad Caliphate, which the Abbasids had overthrown within the decade. The Muslim armies would not launch any major offensive for the next three decades, buying Byzantium precious time to reconsolidate and even take to offensive. Finally, in 863, the Byzantines scored a decisive victory in the Battle of Lalakaon, eliminating the Arab threat and heralding the era of Byzantine ascendancy in the East.

In the early 9th century, the imperial armies confronted a double threat. In the East, the Arab raids continued to threaten Anatolia, while the Bulgars invaded the Byzantine Balkans in the West. In 811, at the Battle of Pliska, the Bulgars inflicted a crushing defeat on the imperial forces, annihilating the whole army, including emperor Nikephoros I. To add insult to injury, the Bulgar khan Krum encased Nikephoros’ skull in silver and used it as a drinking cup. As a result, for the next 150 years, the beleaguered Empire had to refrain from sending the forces northwards, allowing the First Bulgarian Empire to seize control over the Balkans.

The reversal of the Byzantine fortunes came in the 10th century. The emperors of the Macedonian dynasty went on the offensive in the East, strengthened remaining positions in Sicily and southern Italy, and reconquered Crete and Cyprus. However, while they scored several victories over the Bulgars and even destroyed their capital of Preslav, the Macedonian rulers were unable to eliminate their main rival. To make matters worse, by the late 10th century, the Bulgar forces, led by tsar Samuil, renewed hostilities, and after a great victory in 986, restored the powerful Empire.

While the Byzantine emperor, Basil II, made his life aim to destroy the Bulgar state, his attention was drawn to the other more pressing issues. First, the internal revolt and then a war against the Fatimids on the Eastern frontier. Finally, in 1000, Basil was ready to launch an offensive against Bulgaria. Instead of a pitched battle, the Byzantines besieged hostile forts, ravaging the countryside, while the numerically inferior Bulgarians raided Byzantine borderlands. Yet, slowly but methodically, the imperial armies recovered the lost territories and reached the enemy’s territory. Realizing that he was fighting a losing war, Samuil decided to force the enemy into a decisive battle on a terrain of his own choosing, hoping that Basil would sue for peace.

In 1014 a large Byzantine army, 20,000 strong, approached the mountain pass of Kleidion on the Strymon river. Expecting the invasion, the Bulgarians fortified the area with towers and walls. To increase his odds, Samuil, who commanded a larger force (45,000), sent some troops southwards to attack Thessaloniki. The Bulgarian leader expected Basil to send reinforcements. But his plans were foiled by the defeat of the Bulgars, at the hands of local Byzantine troops.

At Kleidion, Basil’s first attempt to take the fortifications also failed, with the Byzantine army unable to pass through the valley. To avoid a lengthy and costly siege, the emperor accepted a plan by one of his generals to lead the small force through a mountainous country and attack the Bulgars from the rear. The plan worked to perfection. On 29th July, the Byzantines surprised the defenders, trapping them in the valley. The Bulgarians abandoned the fortifications to face this new threat, allowing the imperial army to break through the front line and destroy the wall. In the confusion and rout, thousands of Bulgarians lost their lives. Tsar Samuil fled the battlefield but died soon after of a heart attack.

The victory at Kleidion gave Basil II his infamous moniker “Boulgaroktonos” (the Bulgar Slayer). According to the Byzantine historians, after the battle, Basil took dreaded vengeance on the hapless prisoners. For every 100 prisoners, 99 were blinded, and one was left with a single eye to lead them back to their tsar. Upon seeing his mutilated men, Samuil died on the spot. Although this makes for a juicy story, it is probably a later invention used by the imperial propaganda to highlight Basil’s martial exploits over the weaknesses of his civilian successors. Yet, the victory at Kleidion turned the tide of war, with the Byzantines completing the conquest of Bulgaria in the following four years and turning it into a province. The battle also affected the Serbs and Croats, who acknowledged the supremacy of the Byzantine Empire. For the first time since the 7th century, the Danube frontier was under imperial control, together with the entire Balkan peninsula.

By the time Basil II had died in 1025, the Byzantine Empire was once again a great power. In the East, the imperial armies reached Mesopotamia, while in the West, the recent addition of Bulgaria restored the imperial control over the Danube frontier and all of the Balkans. In Sicily, the Byzantine forces were one town away from the reconquest of the entire island. However, Basil II, who spent his whole life waging wars and consolidating the state, left no heir. Under a series of weak and military incompetent rulers, the Empire was weakened. By the 1060s, Byzantium was still a force to reckon with, but the cracks started to appear in its fabric. The constant power games at the court hampered the imperial armies and exposed the eastern frontier. Around the same time, a new and dangerous enemy appeared at the crucial Eastern frontier – the Seljuk Turks.

Having taken the purple in 1068, Romanos IV Diogenes focused on rebuilding the neglected military. Romanos was a member of the Anatolian military aristocracy, well aware of the dangers presented by Seljuk Turks. Yet, the powerful Doukas family opposed the new emperor, considering Romanos a usurper. Romanos’ predecessor was Doukas, and if he wanted to strengthen his legitimacy and eliminate opposition at the court, the emperor had to score a decisive victory against the Seljuks.

In 1071, the opportunity appeared as the Seljuk Turks raided Armenia and Anatolia under their leader, sultan Alp Arslan. Romanos assembled a large force, around 40-50,000 strong, and set out to meet the enemy. However, while the imperial army was impressive in size, only a half were regular troops. The rest was made of mercenaries and feudal levies belonging to frontier landowners of questionable loyalty. Romanos’ inability to fully control these forces played a part in the incoming catastrophe.

After a grueling march through Asia Minor, the army reached Theodosiopolis (modern-day Erzurum), the major center and frontier-town in eastern Anatolia. Here, the imperial council debated the campaign’s next step: should they continue to march into the hostile territory or wait and fortify the position? The emperor chose to attack. Thinking that Alps Arslan was either further away or not coming at all, Romanus marched towards Lake Van, expecting to retake Manzikert (present-day Malazgirt) rather quickly, as well as the nearby fortress of Khliat. However, Alp Arslan was already in the area with 30,000 men (many of them cavalry). The Seljuks may have already defeated the army sent to take Khliat, or the troops fled at the sight of the enemy. Whatever transpired, Romanos was now leading less than half of his original force and was marching into an ambush.

On 23rd August, Manzikert fell to the Byzantines. Realizing that the main Seljuk force was nearby, Romanos decided to act. The emperor rejected Alp Arslan’s proposals, aware that without a decisive victory, the hostile raids could lead to internal revolt and his downfall. Three days later, Romanus drew his forces on the plain outside of Manzikert and advanced. Romanos himself led the regular troops, while the rearguard, composed of mercenaries and feudal levies, was under the command of Andronikos Doukas. Keeping Doukas in a commanding position was an odd choice, considering the dubious loyalties of the powerful family.

The beginning of the battle went well for the Byzantines. The imperial cavalry held off the enemy’s arrow attacks and captured Alp Arslan’s camp by the end of the afternoon. However, the Seljuks proved an elusive enemy. Their mounted archers maintained harassing fire on the Byzantines from the flanks, but the center refused battle. Every time Romanos’ men tried to force pitched battle, the agile enemy’s cavalry wheeled out of range. Aware that his army was exhausted, and the night was closing in, Romanos called for a retreat. His rearguard, however, deliberately pulled back too soon, leaving the emperor without a cover. Now that the Byzantines were thoroughly confused, the Seljuks seized the opportunity and attacked. The right wing routed first, followed by the left. In the end, only the remnants of the Byzantine center, including the emperor and his fiercely loyal Varangian Guard, remained on the battlefield, encircled by the Seljuks. While the Varangians were being annihilated, emperor Romanos was wounded and captured.

The Battle of Manzikert was traditionally considered a catastrophe for the Byzantine Empire. However, the reality is more complex. Despite the defeat, Byzantine casualties were apparently relatively low. Nor were there significant territorial losses. After a week of captivity, Alp Arslan released emperor Romanos in exchange for relatively generous terms. Most importantly, Anatolia, the imperial heartland, its economic and military base, remained untouched. However, Romanos’ death in a battle against treasonous Doukids, and the civil war that followed, destabilized the Byzantine Empire, weakening its defenses at the worst possible time. Within the next few decades, almost all of Asia Minor was overrun by the Seljuks, a blow from which Byzantium would never recover.

Following the chain of disasters at the end of the 11th century, the emperors of the Komnenian dynasty managed to restore the Byzantine Empire’s fortunes. It was not an easy task. To expel the Seljuk Turks from Anatolia, emperor Alexios I had to ask for help from the West, kickstarting the First Crusade. The emperor and his successors maintained a lukewarm relationship with the Crusaders, seeing them as valuable but dangerous allies. The western knights’ military muscle was required to re-establish imperial control over most of Anatolia. Yet, the foreign nobles looked with temptation at the immense wealth of Constantinople. Two years after the violent end of the Komnenian dynasty, its fears were about to be realized.

The tensions between the Byzantines and Westerners began to simmer already under the reign of the last great Komnenian emperor, Manuel I. In 1171, aware that the westerners, especially the Republic of Venice were taking monopoly over the Byzantine trade, the emperor imprisoned all Venetians residing within the imperial territory. The short war ended with no victor, and the relations between two former allies worsened. Then in 1182, the last Komnenian ruler, Andronikos, ordered a massacre of all Roman Catholic (“Latin”) inhabitants of Constantinople. The Normans promptly retaliated, sacking the second largest city – Thessaloniki. Yet, revenge was not the only result of a siege and sack that would bring the Byzantine Empire to its knees. Once again, the internal struggle for power led to a catastrophe.

In 1201, Pope Innocent III called for a Fourth Crusade to reconquer Jerusalem. Twenty-five thousand Crusaders gathered in Venice to embark on the ships provided by doge Enrico Dandolo. When they failed to pay the fee, cunning Dandolo offered a transport in return for seizing Zara (modern-day Zadar), a city on the Adriatic coast, which recently came under the control of the Christian Kingdom of Hungary. In 1202, the armies of Christianity captured and duly sacked Zara. It was in Zara that the crusaders met with Alexios Angelos, a son of the deposed Byzantine emperor. Alexios offered the crusaders a huge sum of money in return for the throne. Finally, in 1203, the horribly side-tracked Crusade reached Constantinople. Following the initial assault, the emperor Alexios III fled the city. The Crusaders’ candidate was installed on the throne as Alexios IV Angelos.

The new emperor, however, grossly miscalculated. The decades of internal struggles, and external wars, had emptied the imperial treasury. To make matters worse, Alexios had no support from the people who considered him a puppet of the crusaders. Soon, the hated Alexios IV was deposed and executed. The new emperor, Alexios V Doukas, refused to honor his predecessor’s agreements, preparing instead to defend the city from the vengeful Crusaders. Already before the siege, the Crusaders and the Venetians had decided to dismantle the old Roman Empire and divide the spoils between them.

Constantinople was a hard nut to crack. Its imposing Theodosian walls had withstood many sieges in their almost thousand-years old history. The waterfront was also well protected by the sea walls. On the 9th of April 1204, the first Crusader attack was repulsed with heavy losses. Three days later, the invaders attacked again, this time from both land and sea. The Venetian fleet entered the Golden Horn and attacked Constantinople’s sea walls. Not expecting ships to approach so close to the walls, the defenders left few men to defend the area. However, the Byzantine troops offered stiff resistance, especially the elite Varangian Guard, and fought to the last man. Finally, on 13th April, the defenders’ will to fight came to an end.

What followed remains the greatest shame ever inflicted by Christians on other fellow Christians, a symbol of betrayal and greed. For three days, Constantinople was a scene of looting and massacre on a massive scale. Then a more systematic looting began. The Crusaders targeted everything, not making a distinction between the palaces and churches. Relics, sculptures, artworks, and books were all stripped away or taken to the crusaders’ homelands. The rest was melted down for coinage. Nothing was sacred. Even the tombs of the emperors, going back to the city’s founder Constantine the Great, were opened up and their precious contents removed. Venice, the main instigator, profited most from the sack. The four bronze horses of the Hippodrome still stand today on the square of Saint Mark’s Basilica in the heart of the city.

The Fourth Crusade never reached the Holy Land. In the following decades, the remaining Crusader’s possession fell in the Muslim hands. Once the most powerful state in the world, the Byzantine Empire was dismantled, with Venice and the newfound Latin Empire taking most of its territory and wealth. But Byzantium would endure. In 1261, it had been re-established again, albeit just as a shadow of its former self. For the rest of its life, the Byzantine Empire would remain a minor power, diminishing in size, until 1453, when the Ottomans took Constantinople for the second and last time.

By 1453, the once-great Byzantine Empire, which had endured for two millennia, consisted of little more than the city of Constantinople and small pieces of land in the Peloponnese and along the southern shore of the Black Sea. What began as a small city on the Tiber and then became the world’s superpower was again reduced to a little slice of territory, surrounded by a powerful enemy. The Ottoman Turks had been seizing imperial lands for two centuries, closing at Constantinople. The last Roman dynasty, the Palaiologans, squandered what little they had of the army in the pointless civil wars. The Byzantines could not count on external support either. After a Polish-Hungarian crusade met disaster at Varna in 1444, there was no further help from the Christian West.

Meanwhile, the young Ottoman sultan prepared for the conquest of Constantinople. In 1452, Mehmed II set his plans in motion, starting the countdown for the doomed city. First, he built the fortress on the Bosphorus and the Dardanelles, isolating the city from relief or supply by sea. Then, to deal with the impregnable thousand-year-old Theodosian walls, Mehmed ordered the construction of the largest cannon yet seen. In April 1453, the large army, 80,000 men strong, and around 100 ships reached Constantinople.

The last Byzantine emperor Constantine XI Palaeologus ordered the famed walls to be repaired in anticipation of the siege. However, the small defending army, 7 000 strong (2000 of them foreigners), knew that if the walls fell, the battle was lost. The task to protect the city was given to Genovese commander Giovanni Giustiniani, who arrived in Constantinople accompanied by 700 western soldiers. The Ottoman force dwarfed the defenders. Eighty thousand men and 100 ships would attack Constantinople in the last siege in the city’s long and illustrious history.

Mehmed’s army laid siege to Constantinople on 6th April. Seven days later, the Ottoman cannons began to bombard Theodosian walls. Soon, breaches began to appear, but the defenders repulsed all the enemy assaults. Meanwhile, the massive chain barrier extended across the Golden Horn prevented the entry of the far superior Ottoman fleet. Frustrated by the lack of results, Mehmed ordered the construction of the log road across Galata, on the northern side of Golden Horn, and rolled their fleet overland to reach the water. The sudden appearance of the massive fleet in front of the sea walls demoralized the defenders and forced Giustiniani to divert his troops from the defense of the city’s land walls.

After the defenders rebuffed his offer for peaceful surrender, on the 52nd day of the siege, Mehmed launched a final attack. The combined sea and land assault began on the morning of 29th May. Turkish irregular troops advanced first but were quickly pushed back by the defenders. The same fate awaited the mercenaries. Finally, the elite Janissaries moved in. At a critical moment, Giustiniani was wounded and left his post, causing a panic among the defenders. The Ottomans then found a small postern gate, accidentally left open – the Kerkoporta – and poured in. According to the reports, emperor Constantine XI died, leading a heroic but doomed counterattack. However, some sources question this, instead saying that the emperor tried to escape. What is certain with Constantine’s death, is that the long line of Roman emperors came to its end.

For three days, the Ottoman soldiers plundered the city and massacred the unfortunate inhabitants. Then the sultan entered the city and rode to the Hagia Sophia, the greatest cathedral in Christendom, converting it into the mosque. Following the prayer, Mehmed II ordered all the hostilities to cease and named Constantinople the new capital of the Ottoman Empire. In the following decades, the city was repopulated and rebuilt, regaining its former importance and glory. While Constantinople prospered, the remnants of the Byzantine Empire struggled until the capture of its last stronghold, Trebizond, in 1461.

The Fall of Constantinople brought an end to the Roman Empire and caused a profound geopolitical, religious, and cultural shift. The Ottoman Empire was now a superpower and would soon become the leader of the Muslim world. Christian kingdoms of Europe had to rely on Hungary and Austria to halt any further Ottoman expansion westwards. The center of Orthodox Christianity shifted north to Russia, while the exodus of Byzantine scholars to Italy started the Renaissance.