What role did the Battle of Manzikert play in causing the Crusades?

The Byzantine Empire and the Seljuk Turks fought over control of eastern Anatolia, where both powers attempted to assert contorl over a region that had important strategic and economic value.

As the Abbasid Caliphate declined during the 10th century, the Seljuks became a powerful Turkish force that adopted Sunni Islam and expanded rapidly into former Persian and Arab lands.

Their military success, combined with a desire to spread Islam and control new territory, brought them into contact with the Byzantine frontier. 

By the 1040s, they raided fortresses, towns, and agricultural communities in Armenia and Cappadocia, which damaged Byzantine provincial administration and disrupted military supply routes.

This reduced the state’s tax revenue and weakened the empire’s defensive network.

In response, the Byzantines tried to reinforce their eastern frontier by restoring old fortifications and granting local commanders authority over military zones.

These measures delayed collapse but failed to reverse Turkish advances. 

After Alp Arslan became sultan in 1063, Seljuk expansion intensified. He not only directed military campaigns into Byzantine-held territory but also supported the migration of Turkmen nomads into the newly raided areas.

This allowed Turkish groups to establish permanent control over key locations, which made future Byzantine counterattacks more difficult.

Romanos IV Diogenes, who assumed the throne in 1068, inherited this worsening crisis and believed that a major military expedition could stop further losses and restore imperial reputation. 

Romanos IV assembled a campaign in 1071 with the goal of pushing the Seljuks out of Armenia and securing the eastern border once more.

He chose to march on the fortress of Manzikert, which had recently fallen under Seljuk control and now was seen as a symbol of Turkish presence in the region.

By targeting this key location, the emperor hoped to demonstrate strength both to the Turks and to political rivals in Constantinople. 

The emperor’s decision to advance into hostile territory came with significant risks.

His army included professional Byzantine soldiers augmented by foreign mercenaries such as Normans and Pechenegs, supported by levies from local provinces that lacked proper training.

Contemporary estimates suggest Romanos commanded an army likely numbering between 30,000 and 40,000 men, while Alp Arslan later confronted him with a mobile force estimated between 15,000 and 30,000 cavalry and mounted archers.

However, political divisions within the imperial court had already weakened the loyalty of many commanders, and several had ties to rival noble families that opposed Romanos’ rule.

These internal tensions made it difficult to coordinate operations and placed the emperor in a vulnerable position should the campaign fail. 

Nevertheless, Romanos committed a strategic error by dividing his army in order to attack both Manzikert and the nearby fortress of Akhlat, which weakened his main force and created supply difficulties, and slowed his advance while exposing his troops to Turkish ambushes.

Alp Arslan had been campaigning in the south and was negotiating a potential truce, but quickly redirected his forces and marched north with a mobile army of cavalry and archers.

The Seljuk sultan moved swiftly, surprising the Byzantines and forcing Romanos into a battle on unfavourable terrain near Lake Van. 

On 26 August 1071, the Byzantine army engaged the Seljuk forces near the fortress of Manzikert, where both sides prepared for battle on open ground surrounded by hills.

Romanos placed his troops in standard formation with a central line, two wings, and a rear reserve.

He advanced cautiously and attempted to draw the Seljuks into a direct confrontation, but Alp Arslan avoided this by using his mounted archers to harass the Byzantine lines. 

The Seljuks executed a series of feigned retreats which drew the Byzantines forward and stretched their formation across the plain.

As the day progressed, the constant movement of Turkish cavalry wore down the Byzantine troops.

These soldiers struggled to respond to the fast-paced attacks and they found it hard to maintain unity.

Some units began to lose contact with the main line, and commanders found it difficult to relay orders or regroup their forces under pressure. 

In the late afternoon, Romanos ordered a withdrawal to regroup, but many of his subordinates misunderstood the signal or disobeyed his commands entirely.

The lack of discipline in parts of the army led to a breakdown in formation, and the decision of General Andronikos Doukas to abandon the battlefield further collapsed the Byzantine position.

Doukas was the son of Caesar John Doukas and a bitter opponent of Romanos, and he commanded the reserve that could have stabilised the retreat, but instead withdrew his forces from the battlefield.

This was widely interpreted as politically motivated sabotage. His betrayal, likely motivated by internal court rivalries, caused panic among the Byzantine ranks. 

The Seljuks seized the opportunity to surround the disorganised Byzantine centre and launched a final attack that broke Romanos’ line.

The emperor fought on and sustained injuries before being captured and taken to Alp Arslan, who spared his life and negotiated a ransom.

The defeat left thousands of soldiers dead or scattered, and the Byzantine campaign ended in complete failure. 

The defeat at Manzikert destroyed Byzantine military authority in Anatolia and showed the empire to further Turkish advances.

Romanos returned from captivity only to be overthrown by his political enemies, who blinded and imprisoned him soon after.

The Doukas family, now back in control, used the defeat to justify their growing control.

The gap in authority in Constantinople led to a series of civil wars, as rival generals and court factions fought for control.

This internal instability crippled the empire’s ability to organise resistance to further Turkish attacks. 

Over the next decade, Turkish warlords and wandering tribes moved west and took control of former Byzantine territory across the Anatolian region.

The empire lost key cities and agricultural lands and saw its military outposts, many of which were abandoned or taken without a fight.

One of the most significant warlords, Suleiman ibn Qutulmish, established the Sultanate of Rum around 1077, though its official approval came after his death in 1086, which created a permanent Turkish state in central Anatolia.

The movement of Turkmen tribes into these areas established settlements that gradually altered the population and political make-up of the region. 

The loss of Anatolia, which had been the empire’s main source of grain and soldiers and which provided its tax revenue, cut off Constantinople and left it at risk.

Emperor Alexios I Komnenos, who came to power in 1081, tried to bring back order by changing the army and securing alliances.

He also sent representatives to western Europe to request military aid, which began with the Council of Piacenza in March 1095, where Byzantine representatives asked for help from Pope Urban II.

Alexios hoped that Latin knights could help recover lost territory when trained soldiers served under his command. 

This appeal would be a major change in Byzantine relations with the west, as it brought the pope and western nobility into direct contact with the eastern empire’s crisis.

Alexios hoped for professional mercenaries, but what followed exceeded his expectations and changed the political and religious situation of the eastern Mediterranean. 

The Battle of Manzikert exposed the vulnerability of the Byzantine Empire and gave the papacy a chance to strengthen its religious leadership and political standing in Christian affairs outside western Europe.

When Pope Urban II received Alexios’ appeal in the 1090s, he recognised a chance to bring together the divided nobility of Latin Christendom and direct their aggression into a holy war against the Muslim powers who now occupied former Christian lands. 

At the Council of Clermont on 27 November 1095, the pope called for a Crusade to aid eastern Christians and liberate Jerusalem.

The goal of reclaiming the Holy City quickly captured public attention, as Urban framed the conflict as a defensive response to Muslim aggression against fellow Christians.

The loss of Anatolia and the weakness of Byzantium was used as evidence that Christian lands faced a serious threat and required immediate action. 

Knights, nobles, and commoners from across Europe responded enthusiastically, motivated by religious devotion, by land and wealth, and encouraged by the promise of papal forgiveness for sins.

Many believed they were defending the faith and restoring order to a region they viewed as threatened by Muslim expansion and imperial weakness.

Others saw a chance to establish new territories under their own leadership. The First Crusade, which began with the People's Crusade in spring 1096, saw the main armies arrive at Constantinople by early 1097, where they began a complicated and often uncertain collaboration with Byzantine forces. 

The defeat at Manzikert did not directly bring about the Crusades, but instead created the conditions in which a call to arms became both convincing and urgent.

The collapse of Byzantine power in Anatolia and the appeal for western aid convinced the papacy that military intervention would have both religious and political goals.

As a result, the First Crusade departed for the east in 1096 and had followed directly from the chain of events that began with the disaster at Manzikert.