What did the European Christians do to try to free Palestine from Muslim control?

The First Crusade was launched in 1095 by Pope Urban II with the dual goals of conquering the sacred city of Jerusalem and the Holy Land and freeing the Eastern Christians from Muslim rule. What started as an appeal by Byzantine Emperor Alexius I Comnenus for western mercenaries to fight the Seljuk Turks in Anatolia quickly turned into a wholesale Western migration and conquest of territory outside of Europe. Both knights and peasants from many nations of Western Europe travelled over land and by sea towards Jerusalem and captured the city in July 1099, establishing the Kingdom of Jerusalem and other Crusader states. Although these gains lasted for less than two hundred years, the First Crusade was a major turning point in the expansion of Western power, as well as the first major step towards reopening international trade in the West since the fall of the Western Roman Empire.