The Crusades were a series of intermittent military campaigns sanctioned by various Popes in the Middle Ages, from 1096 to 1487. In 1095, Byzantine Emperor Alexios I sent an ambassador from Constantinople to  Pope Urban II in Italy requesting military support in the conflict with the eastward invading Turks. The Pope responded promptly by calling Catholic soldiers to join the First Crusade. The immediate goal was to guarantee pilgrims access to the holy sites in the Holy Land that were under Muslim control. His long-range goal was to reunite the Eastern and Western branches of Christendom after their split in 1054, with the pope as head of the united Church. A complex 200-year struggle ensued.