Pope Urban II proclaimed the first crusade in 1095 with the goal of restoring Christian access to the holy places in and near Jerusalem.
First off, a great deal of cultural diffusion took place which precipitated the exchange of ideas, resources, materials and technology.
This struggle for control of the Holy Land went on for 200-years and ended in failure.
Although the Christians failed to reclaim their Holy Land, a number of important cultural shifts transpired.
Initially, Muslims did very little about the Crusader states due to internal conflicts.
Second, a significant shift in power took place throughout Europe. Monarchs gained more power, and the collective identity of the Latin Church was consolidated under the Pope’s leadership.
The First Crusade unleashed a wave of Christian fury that was expressed in the massacres of Jews that accompanied and preceded the movement of the crusaders through Europe, including the massacre of 8,000 Jews in the Rhineland, as well as the violent treatment of the “schismatic” Orthodox Christians of the east.
These states reopened the Mediterranean to trade and travel enabling Genoa and Venice to flourish.
The official crusader armies for the First Crusade set off from France and Italy at different times in August and September 1096. The western forces may have totaled as many as 100,000 people.
As a result of the First Crusade, four main Crusader states were created: the County of Edessa, the Principality of Antioch, the County of Tripoli and Kingdom of Jerusalem.
They were unsuccessful and on 15 July 1099 the crusaders entered the city.
On the other side of the Mediterranean, however, the Second Crusade met with great success as a group of Northern European Crusaders stopped in Portugal, allied with the Portuguese King, Afonso I of Portugal, and retook Lisbon from the Muslims in 1147.
Pledging to restore lost territories to the empire, the main army, mostly French and Norman knights under baronial leadership marched south through Anatolia.
Imad ad-Din Zengi began to retake territory from the Christians, beginning with Aleppo in 1128. He retook Edessa in 1144.
Fourthly, the crusades were the source of heroism, chivalry and medieval piety that grew medieval romance, philosophy and literature.
Thirdly, the European social structure changed as women gained increased rights and the middle class gained power.
The first two crusades were followed by five more major Crusades against Muslim territories in the east and numerous minor ones.
The Jews and Muslims fought together to defend Jerusalem against the invading Franks.
The armies journeyed eastward by land toward Constantinople, where they received a wary welcome from the Byzantine Emperor.
The crusaders proceeded to massacre the remaining Jewish and Muslim civilians and pillaged or destroyed mosques and the city itself.
Eventually, the Muslims began to reunite under the leadership of Imad ad-Din Zengi, who was appointed governor of Mosul in 1127.
French and South German armies marched to Jerusalem in 1147 but failed to win any major victories.
