Given the underlying factors, how the Crusades affect the Byzantine Empire is evident. Though the Crusades are assumed to be wars of righteousness or religious fervor, nothing holy or reverent occurred during the atrocities that hastened the Byzantine decline.

Keep on reading if you want to find out all the ways that the crusades contributed to the fall of the Byzantine Empire.

How Did the Crusades Contribute to the Fall of the Byzantine Empire?

So brutal was the Crusader attack on Constantinople in 1204 that it ripped the sister religions apart, creating a bitter, grudge-fueled mistrust that lasted until modern times. The devastation was such that the Byzantine empire never truly recovered.

However, the seeds for the decline of Byzantine Empire existed long before the Crusades began. The split of the Roman Empire into East and West created resentments and jealousies that led to the division between the Roman Catholic and Eastern Orthodox Churches.

Moreover, crippling the largest Christian city in Europe was a big mistake for the Roman Catholics. With the Byzantine Empire in tatters, there was no barrier between the Christian World and the invading Muslims. As the rogue Crusaders helped the Byzantine Empire end, they also aided the future conquests of the Ottoman Turks into Europe.

Setting the Stage: A Quick Synopsis of Byzantine History

Around 285 CE, Emperor Diocletian decided that the Roman Empire was too large to control alone. He named a Caesar to rule the West while he governed the East’s wealthier, more civilized areas. In 330 CE, his successor, Constantine, moved the capital to Byzantium in Greece and renamed it Constantinople.

Though they still considered themselves Romans, the Byzantine culture developed quite differently from its neighbor, adopting new secular and religious practices. They even adopted Greek as their native language instead of Latin.

Unfortunately, differences can breed fear and contempt, which is exactly what happened in the case of the Byzantine empire.

When Pope Leo crowned Charlemagne as the Holy Roman Emperor in 800, the Byzantines were insulted; they considered themselves Europe’s primary economic and religious power. Over the following centuries, the disagreements and dissent continued until most Eastern Orthodox churches refused to acknowledge the Pope as their spiritual leader.

Naturally, this fueled further mistrust between Byzantium and the Roman Catholics in the West.

The First Crusade: Uneasy Allies in Religious Warfare

In the 11th Century, the Muslim conquests in the East reached the edges of the Byzantine Empire. The Seljuk Turks conquered Anatolia and threatened to continue West. So, in 1095, the Byzantine emperor Alexios I reluctantly asked Pope Urban II for assistance. Despite the bruised feelings between Rome and the Byzantines, the Pope readily agreed, since the fall of Byzantium would leave his own regions vulnerable to a Muslim attack.

The first wave of the First Crusade swept across Europe, pillaging towns on the way to replenish their supplies. This behavior displeased Byzantine leaders, especially when they had to stop looting parties in Constantinople itself. When the undisciplined Crusaders finally reached Anatolia, the Turkish army crushed them.

Nobles and their followers populated the second wave. When they reached Constantinople, they expected Alexios I to support their large numbers. Alexios distrusted the Crusaders since some of their leaders had attempted large-scale invasions against the Byzantines in the past.

Somehow, Alexios managed to safely usher the army across the Bosporus to engage with the Turks.

This time, the Crusaders won back several Byzantine cities. The army then swept East to Antioch and Jerusalem and secured the region by 1099. Though the Crusade was initiated as a religious endeavor, the principalities established by the Crusaders were strangely secular. Still, the victory was credited to Rome and the Church.

The Second and Third Crusades: Byzantium Gets the Blame

The Holy Land soon returned to Muslim hands. Though the Byzantine Empire remained a Christian stronghold, they achieved a fragile truce with the Seljuk and the Ottomans. The truce safeguarded the Byzantine territories and also increased trade in the region, from which both sides prospered.

However tenuous, this truce was viewed by the Romans as a betrayal of Christianity. When both the Second and the Third Crusades failed, the Byzantines received a healthy share of the blame for fraternizing with the enemy and neglecting to send troops, or more importantly, funds.

The animosity between East and West resulted in continued insults, betrayals, jealousy, and suspicion, reaching a peak around the time Pope Innocent III called for the Fourth Crusade at the turn of the century.

The Fourth Crusade: A Strange Detour to Constantinople

The Crusaders, under Alexios IV, ordered 240 Venetian ships to transport the army. Unfortunately, England, France, and Germany had issues at home, and they sent few troops or funds. The Venetians demanded an exorbitant sum for the finished ships, and the Crusaders could not pay.

The Venetians agreed to delay payment and join the Crusade in exchange for stopping on the way to reconquer the town of Zara. Enraged by their attack on a Christian city, the Pope excommunicated them all, but he soon relented. A few hundred Crusaders also objected and broke away to continue to the Holy Land. These were the only Crusaders that finished the journey.

Why the rest of the Crusaders then veered toward Constantinople is still a subject of debate among scholars. Religious differences and the animosity between East and West were undoubtedly factors, as were the economic advantages. Some Crusader leaders, such as the Doge Enrico Dandolo, harbored more personal grudges and attacking Constantinople provided them a way to seek revenge.

The Siege and Sack of Constantinople: Brutality and Cowardice

On June 23, 1203, the sidetracked Crusaders and Venetians reached Constantinople and laid siege to the city. After a few months, the Byzantines surrendered, and Alexios III fled by night, taking half a ton of gold and jewels from the treasury.

First Attack on Constantinople: The Aftermath

Isaac II Angelos and his son Alexios IV became co-emperors. However, with the coffers depleted, Alexios IV still couldn’t pay the Venetians or the Crusaders as promised. He melted down valuable icons from both the Roman and Byzantine churches for their silver and gold, but it wasn’t enough.

Desperate, Alexios IV begged for more time and took a small army to track down Alexios III and the stolen gold. While he was gone, riots erupted between the Byzantines and the Crusaders, eventually leading to the Great Fire that devastated a significant portion of Constantinople.

Second Attack on Constantinople: The Byzantines Defeat

By January 1204, Isaac II died, and the Byzantines elected Alexios Doukas, who became Alexios V. He easily defeated, captured, and executed Alexios IV in February.

Unfortunately, the Crusaders demanded that Alexios V keep his predecessor’s bargain. When he refused, the Crusaders once again attacked the city, but the Byzantines defeated them this time.

Third Attack on Constantinople: The Sack of the City

Though Pope Innocent III objected, the Latin clergy used political rhetoric to energize the Crusaders for another attack. The Venetians joined in by sea, and the city’s defenses began to crumble.

Alexios V fled as well, and no noble mustered enough support to assume the throne. With no working government to pay them, the mercenaries defending the city simply gave up the fight.

The sack of Constantinople began on April 12, 1204. For three days, the Crusaders and the Venetians looted or destroyed countless priceless art and religious relics, defiled churches, and raped and murdered the clergy. Citizens of all classes and backgrounds suffered and died violently.

These Crusaders vowed to fight for God, and they ended by revenging their own petty and sometimes imagined grudges in most violent ways. Pope Innocent III spoke of the incident with great regret.

Failure of the Fourth Crusade and Fragmentation of Byzantium

The few hundred Crusaders that bypassed Constantinople and arrived at the Holy Land were far too few to be effective. So, the Fourth Crusade was a failure, and it solidified the rift between the Roman Catholics and the Greek Orthodox.

The rogue Crusaders and the Venetians established the Latin Empire of Constantinople, while a few remaining Byzantine factions founded the states of Nicaea, Epirus, and Trebizond. In 1261, the state of Nicaea did retake Constantinople, but the victory was short-lived.

The Empire never regained its former wealth or power. The few remaining cities slowly dissolved under the advancing Ottoman Empire, which claimed Constantinople in 1453, renaming it Istanbul.


The fall of the Byzantine Empire directly resulted from the barbaric events that occurred during the Fourth Crusade.

Here’s a reminder of the main facts we mentioned:

  • In 285 CE, the Roman Empire split in two for easier governance
  • Differences in social and economic development fostered mistrust between the two thriving Empires
  • The Seljuk Turks invaded and conquered Anatolia, prompting the two empires to join together to defend the region, thus beginning the First Crusade
  • Though the First Crusade was eventually successful, it did nothing to mend relations between Rome and the Byzantines
  • The Fourth Crusade was rife with vengeful, selfish acts that had little to do with saving the Christian world from Islam
  • The sack of Constantinople by the Crusaders was the death knell for the Byzantine Empire

In a way, Alexios I began the decline of the Byzantine Empire by supplying the Pope with a catalyst for the Crusades. Little did he know that his simple request for assistance would lead to the downfall of one of the greatest civilizations in European History.


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