How did pope Urban II respond to the Seljuk Turks?

Answer 1

Pope Urban made a very public and urgent plea in 1095 to all of Christendom after receiving a letter from the Byzantine Emperor Alexis describing the increasing danger from the Seljuk Turks, Tartars from Asia, who had already conquered the caliphate of Baghdad in 1055 and now were seeking to expand their empire into the Holy Land. All of the history you have heard about the Crusades is so much hogwash:

from Seven Lies About Catholic History, by Diane Moczar

Unprovoked Muslim aggression in the seventh century brought large parts of the southern Byzantine Empire, including Syria, the Holy Land, and Egypt under Arab rule. Christians who survived the conquests found themselves subject to a special poll tax and discriminated against as an inferior class known as dhimmi. Often their churches were destroyed and other harsh conditions imposed. For centuries their complaints had been reaching Rome, but Europe was having its own Dark Age of massive invasion, and nothing could be done to relieve the plight of eastern Christians.

By the eleventh century, under the rule of a new Muslim dynasty, conditions worsened. The Church of the Holy Sepulcher, site of the Crucifixion was destroyed, along with a large number of other churches, and Christian pilgrims were massacred. In 1067 a group of seven thousand peaceful German pilgrims lost two-thirds of their number to Muslim assaults. By this time the popes, including St. Gregory VII, were actively trying to rally support for relief of eastern Christians, though without success. It was not until the very end of the century, in 1095, that Pope Urban's address at Clermont in France met with a response-though not quite the one he had hoped for. But the response was what we now call the First Crusade.

"The general consensus of opinion among medievalists . . . is tha thte Crusades were military expeditions organized by the peoples of Western Christendom, notably the Normans and the French, under the leadership of the Roman Popes, for the recover of the Holy Places from their Muslim masters." This seems to sum up most neatly what the Crusades really were and how their participants actually viewed them. The Crusades were not colonialist or commercial ventures, they were not intended to force Christianity on Jews and Muslims, and they were not the projects of individual warlords. Their primary goal, in addition to the defense of the Eastern Empire, was the recovery of the Holy Land for Christendom, and they acknowledged the leadership of the Popes. As French historian Louis Brehier wrote, 'the popes alone understood the menace of Islam's progress for christian civilization.'"

Answer 2

The Seljuk Turks were a common enemy, and because he wanted to reclaim the Holy Land (Jerusalem)