After the loss of Jerusalem in 1187, some merchants from Lübeck and Bremen took up the idea and founded a field hospital for the duration of the Siege of Acre in 1190, which became the nucleus of the order; Celestine III recognized it in 1192 by granting the monks Augustinian Rule. However, based on the model of the Knights Templar, it was transformed into a military order in 1198 and the head of the order became known as the Grand Master ("magister hospitalis"). It received papal orders for crusades to take and hold Jerusalem for Christianity and defend the Holy Land against the Muslim Saracens. During the rule of Grand Master Hermann von Salza (1209–1239) the Order changed from being a hospice brotherhood for pilgrims to primarily a military order.