What were the causes of the First Crusade?

In the 11th century, the Byzantine empire was in decline. They were fighting against the Muslim Seljuk Turks, who were slowly taking over their land.

In particular, the Seljuk forces had been encroaching on Byzantine territories in Asia Minor.

In 1071, the Byzantine emperor, Romanos IV Diogenes, raised an army and marched east to fight off the invaders.

Romanos' forces were primarily made up of mercenaries, who had signed up just for the pay.

However, when these mercenaries saw the Seljuk forces, they retreated from the battlefield, leaving the emperor and his forces to fight for themselves.

The Battle of Manzikert took place on the 26th August 1071. The Byzantines suffered a heavy defeat and, what was considered much worse at the time, Emperor Romanos was captured by Seljuk Turks.

Following their victory, the Seljuk created the Sultanate of Rûm which held control over much of Asia Minor.

As a result, the Byzantines lost a significant amount of land and the income they generated, which made their empire much weaker. 

Also, the Byzantines had to pay a huge sum of money and surrender even more regions in order to secure the return of Romanos.

However, when the emperor returned to the capital city of Constantinople, he realised he had lost the confidence of many people.

Ultimately, a civil war would remove Romanos from power.

In 1081, a new Byzantine ruling dynasty, and a new emperor, Alexios I Comnenus, came to power.

He realized that he needed help from the west if he wanted to recapture Asia Minor.

Alexios sent envoys to western Europe in the early 1080s, asking for help against the Seljuks.

However, his appeals went unanswered. In fact, many western Europeans saw the Byzantines as their enemy because they were not part of the Catholic Church. 

Then, Alexios tried a different approach and sent a personal appeal to Pope Urban II in March of 1095.

When the pope received the messengers, he was busy at the Council of Piacenza in northern Italy, where he was meeting with church leaders to help resolve disputes in Europe.

While the pope didn't respond to the request immediately, he apparently saw Alexios' call for help as an opportunity to solve some ongoing problems he was facing. 

In November of that same year, Urban II travelled to France, where he was due to attend another church council.

This time, it was in the French town of Clermont and it was called to both deal with internal church matters and to discuss Alexios' request.

Urban asked the bishops and abbots he invited to the council, to bring along with them the most important lords of their regions. 

The Council was held from November 18 to November 28, and about 300 church leaders from all of France attended.

On the second last day of this council, the pope gave a speech in which he talked about the need to defend Christianity and liberate the Holy Land from Muslim control.

This was the official declaration of the start of the First Crusade.

Pope Urban II's speech that called for the First Crusade is one of the most famous causes of this event. Five different versions of his speech survive.

They are written by people who were either at the council or heard about it from others.

They include the anonymous Gesta Francorum ('The Deeds of the Franks'), Fulcher of Chartres, Robert the Monk, Baldric (the archbishop of Dol), and Guibert de Nogent.

In his speech, the pope talked about the Seljuk Turks and how they had threatened Byzantine land, desecrating the Holy Land, and were mistreated Christian pilgrims.

He also asked for western European knights to take up arms and fight in what he called a "just war".

The reasons given by Pope Urban II for launching the First Crusade were mostly based on religious grounds.

He believed that it was God's will that Christians recapture the Holy Land, and he used this as justification for asking people to go on this dangerous campaign. 

Fulcher claims that Urban addressed the lack of compliance with the Peace of God. He then urged both rich and poor Christians from western Europe to assist the Greeks in the east, since "Deus vult," ("God wills it"), was his rousing call to arms at the conclusion of his final speech.

However, there were also political reasons for launching the First Crusade. By helping the Byzantines, Pope Urban II hoped to gain their support against the Germanic emperors who were threatening his power.

One of the most famous elements of Urban's encouragement for Christian rulers to go on crusade involves an offer of spiritual benefits.

Fulcher's version of the speech specifically mentions the pope's promise that those who die on crusade will have their sins forgiven. 

While it's impossible to know exactly what Urban II said during his speech, it's clear that he promised some sort of spiritual benefit for those who took up arms against the Muslims.

This offer of forgiveness was likely a strong incentive for many people to go on crusade. 

It's also worth noting that the concept of crusading wasn't new in the 11th century. In fact, papal bulls (official documents) had been issued in the past calling for Christians to fight against Muslims in Spain and Sicily.

However, these were limited campaigns and didn't involve large numbers of people from all over Europe. 

Following the Council of Clermont, Urban focused on Crusade preaching in France and papal legates propagated the word throughout Southern Italy.

The response to this speech was overwhelmingly positive. Many people in attendance, including some of the most powerful lords of France, swore an oath to go on crusade.

They took this vow seriously and began making preparations to leave for the east as soon as possible.

One of the most powerful leaders in France, Raymond, the count of Toulouse, pledged to take part in the crusade.

However, many people believed that the pope had met with him before the council to secure his participation.

Once Raymond had made his commitment public knowledge, other leaders would most certainly sign up as well.

The First Crusade was now official and over the winter months, leaders from France and Germany would gather their forces together in preparation for the long march to the Holy Land.