A. Urban II
These incursions prompted the emperor of Byzantium, Alexius I Comnenus to send a delegation to Piacenza, Italy, asking Pope Urban II in March 1095 for help against the Turks. On November 27, 1095, in Clermont, France, Pope Urban II called for a crusade to help the Byzantines and to free the city of Jerusalem.
Answer;
Nationalism convinced the people of Europe that their own nation could take on any military threat. This was a role nationalism played in the outbreak of world War I.
Explanation;
Nationalism reached a fevered pitch in Europe prior to the first World War. As a political tool, it was the belief that European technological, cultural, economic and military superiority was the cause for the subjugation of more backward economies and cultures.
The pan-Slavic nationalism inspired the assassination of Archduke Franz Ferdinand in Sarajevo in June 1914, an event that led directly to the outbreak of World War I.
By the time World War II ended, most American officials agreed that the best defense against the Soviet threat was a strategy called “containment.” In his famous “Long Telegram,” the diplomat George Kennan (1904-2005) explained the policy: The Soviet Union, he wrote, was “a political force committed fanatically to the belief that with the U.S. there can be no permanent modus vivendi [agreement between parties that disagree].” As a result, America’s only choice was the “long-term, patient but firm and vigilant containment of Russian expansive tendencies.” “It must be the policy of the United States,” he declared before Congress in 1947, “to support free peoples who are resisting attempted subjugation…by outside pressures.” This way of thinking would shape American foreign policy for the next four decades.