The Knights Hospitaller (the Order of Knights of the Hospital of St. John of Jerusalem or Knights of Malta or Knights of Rhodes) is a tradition which began as a Benedictine nursing Order founded in the 11th century based in the Holy Land, but soon became a militant Christian Chivalric Order under its own charter, and was charged with the care and defence of pilgrims. Following the loss of Christian territory in the Holy Land, the Order operated from Rhodes, of which it was sovereign, and later from Malta as a vassal state under the King of Sicily. The mediæval Order can be said to have come to an end following its ejection from Malta by Napoleon. The Sovereign Military Order of Malta (see below) is the main successor to this tradition.
In 600, Abbot Probus was commissioned by Pope Gregory the Great to build a hostel in Jerusalem to treat and care for Christian pilgrims to the Holy Land. In 800, Charlemagne, Emperor of the Holy Roman Empire, enlarged Probus' hostel and added a library to it. Unfortunately, about 200 years later, in 1005, Caliph El Hakim, a fanatic who demanded that his subjects worship him as a god, destroyed the hostel in addition to 3000 other buildings. He made the Christians wear wooden crosses, half a metre long by half a metre wide, around their necks. Although Christians were not allowed to buy slaves, male or female, and had few other privileges, they were allowed to ride horses on the condition that they ride with wooden saddles and unornamented girths. Ironically, El Hakim's mother was Christian. In 1023, merchants from Amalfi and Salerno in Italy were given permission by the Caliph Haroun el Raschid of Egypt to rebuild the hospice in Jerusalem. The hospice, which was built on the site of the monastery of Saint John the Baptist, took in Christian pilgrims traveling to visit the birthplace of Jesus. It was served by Benedictine Brothers.
The monastic hospitaller order was founded following the First Crusade by the Blessed Gerard, whose role as founder was confirmed by a Papal bull of Pope Paschal II in 1113. Gerard acquired territory and revenues for his order throughout the Kingdom of Jerusalem and beyond. His successor, Raymond du Puy of Provence, established the first significant Hospitaller infirmary near to the Church of the Holy Sepulchre in Jerusalem. Initially the group just cared for those pilgrims who made it to Jerusalem but the order soon extended into providing an armed escort to pilgrims. The escort soon grew into a substantial force.
Together with the Knights Templar, who were formed later in 1119, they became one of the most powerful Christian groups in the area. The order came to distinguish itself in battles with the Muslims, its soldiers wearing a black surcoat with a white cross. By the mid-12th century, the order was clearly divided into military brothers and those who worked with the sick. It was still a religious order and had useful privileges granted by the Papacy, for example, the order was exempt from all authority save that of the Pope, and it paid no tithes and was allowed its own religious buildings. Many of the more substantial Christian fortifications in the Holy Land were the work of either the Templars or Hospitallers, at the height of the Kingdom of Jerusalem the Hospitallers held seven great forts and 140 other estates in the area. The two largest of these, their bases of power in the Kingdom and in the Principality of Antioch, were Krak des Chevaliers, and Margat, both located near Tripoli. The property of the Order was divided into priories, subdivided into bailiwicks, which in turn were divided into commanderies.