On this day in 1096, the armies of the First Crusade officially set out for the Holy Land. They were responding to Pope Urban II's call the previous November for people of the faith to travel to Jerusalem and liberate the Church of the Holy Sepulchre from the Muslims. The pope chose August 15 because it is the date of the Feast of the Assumption.

His armies were preceded by the so-called People's Crusade, which was organized several months earlier by the itinerant preacher Peter the Hermit and decimated by the Seljuks in Anatolia before ever making it to Jerusalem.

While reclaiming Jerusalem was the pope's nominal goal, he was also responding to an appeal for help from Alexios I Komnenos, the Byzantine emperor in Constantinople, who too was fighting off Seljuk Muslims from the east. Only on June 7, 1099, the pope's Crusaders, led by Raymond of Toulouse, Robert of Normandy and Tancred, arrived in Jerusalem, which the Fatimids of Egypt had by then wrested from Seljuk control. After a siege of more than a month, the Crusaders conquered Jerusalem on July 15. Their new Kingdom of Jerusalem lasted until it was routed – almost completely – by Saladin in 1187. The Crusades continued until early in the 14th century.