The First Crusade
The First Crusade was a military expedition by European Christians against Muslim territory in the Levant, which resulted in the capture of Jerusalem in 1099.
It was launched in 1095 by Pope Urban II with the primary goal of responding to the appeal from Byzantine Emperor Alexius I. The Emperor requested that western volunteers come to their aid and repel the Seljuk Turks from Anatolia, modern day Turkey. An additional goal soon became the principal objective—the Christian reconquest of the sacred city of Jerusalem and the Holy Land and the freeing of the Eastern Christians from Islamic rule.
Both knights and peasants from many nations of Western Europe traveled over land and by sea first towards Constantinople (modern day Istanbul) and then towards Jerusalem; however, the numbers of the peasants completely outnumbered the numbers of the knights. As the peasants and knights were split in different armies, only the knights' army reached Jerusalem. Once there, the crusaders set up a siege and captured the city in July 1099, establishing the Kingdom of Jerusalem, County of Tripoli, the Principality of Antioch, and the County of Edessa.
Although these gains lasted for less than two hundred years, the First Crusade was part of the Christian response to the Islamic conquests, as well as the first major step towards reopening international trade in the West since the fall of the Western Roman Empire.