After the death of Charlemagne in 814 and the eventual collapse of his empire, Europe was under attack and on the defensive. Nomadic people from Asia pillaged eastern and central Europe until the 10th century. Beginning about 800, several centuries of Viking raids disrupted life in northern Europe and even threatened Mediterranean cities. But the greatest threat came from the forces of Islam. Eventually these threats became real. Battles broke out and these battles turned to wars spanning from 1095 to 1229; all this over one city, Jerusalem, on country, Israel, one land, the Holy Land.
Islamic forces had already conquered North Africa, the eastern shores of the Mediterranean, and most of Spain by the 8th century. They also established bases in Italy, greatly reduced the size and power of the Byzantine Empire, and took over its capital, Constantinople. Islam was spreading even faster than the Islamic army was conquering. The five pillars of Islam appealed to many, as did the Koran and the founder of Islam, Muhammad. Eventually, Islam posed a threat of a rival culture and religion which seemed appealing and unstoppable. By the 11th century the balance of power began to swing toward the West. The church became more centralized and stronger from a reform movement to end the practice of kings installing important clergy, such as bishops, in office. Popes were able to effectively unite European popular support behind them. This greatly contributed to the popular appeal of the first Crusades. Europe's population was growing, its urban life was beginning to revive, and both long distance and local trade were gradually increasing. European human and economic resources could now support new enterprises on the scale of the Crusades. A growing population created more wealth therefore meant a greater demand for goods from elsewhere. Thus worldly interests coincided with religious feelings about the Holy Land and so the crusades began.
Pope Urban II, in a speech at Clermont in France in November 1095, called for a great Christian expedition to free Jerusalem from the Turks, a new Muslim power that had recently begun actively harassing peaceful Christian pilgrims traveling to Jerusalem. These factors were genuine causes, and at the same time, useful justifications for the pope's call for a Crusade. As a result, Urban's speech appealed to thousands of people of all classes. This started the First Crusade.
The First Crusade was successful in freeing Jerusalem. It also established a Western Christian military presence in the Near East that lasted for almost 200 years. The First Crusade attracted no European kings. They came primarily from the lands of French culture and language. These Crusaders faced many obstacles. They had no obvious or widely accepted leader, no relations with the churchmen who went with them, no definition of the pope's role, and no agreement with the Byzantine emperor on whether they were his allies, servants, rivals, or perhaps enemies....