The Knights Hospitaller were an order of religious and then military protectors of Christians pilgrims in the Holy Land in the Middle Ages.

Muslim armies had conquered the city of Jerusalem in the 7th Century. The city was sacred to Christians and Jews, as well as to Muslims, and many Christians made a habit of making a pilgrimage to Jerusalem to visit sites associated with Jesus, the founder of Christianity.

In 1048, the Caliph of Egypt gave permission for businessmen from Italy's Republic of Amalfi to build a church, a convent, and a hospital in Jerusalem. When Western forces took Jerusalem in 1099, during the First Crusade, they established the Kingdom of Jerusalem, one of four Crusader States.

The leader at this time of the hospital established by the Amalfi businessmen was Gerard. He oversaw the construction of other hospitals on the routes most traveled by Christians traveling to the Holy Land. Such travel was exhausting and harsh, and many people fell ill on the way to or from Jerusalem.

An order from Pope Paschal II in February of 1113 established the Knights Hospitaller. The official name was the Order of Knights of the Hospital of Saint John of Jerusalem. (The first hospital had been founded within the walls of the Monastery of Saint John the Baptist, which predated and survived the Muslim occupation.)

Recruits came from all over Europe and were expected to practice piety, chastity, and poverty. They wore a black robe that had on the front a white eight-pointed cross. They signed up for a lifetime commitment.

Travel to the Holy Land became increasingly treacherous, and the Catholic Church in 1119 established another order to assist pilgrims, the Knights Templar. This order was set up with a military focus, and Templar knights provided protection for people making pilgrimages to Jerusalem and elsewhere in the Holy Land.

Not long after the establishment of the Knights Templar, the Knights Hospitaller added military support to their job descriptions. They did not abandon their caregiving duties, however. The order had three ranks: knight, chaplain, and serving brother. This was under the leadership of Gerard's successor, Raymond de Puy.

Control of Jerusalem swung back to Muslim armies after the 1187 campaigns of the famed warrior-sultan Saladin. Muslim reoccupation of the Crusader States continued. Beginning with the Third Crusade, Knights Hospitaller fought alongside Crusaders.

The order also set about taking control of castles that guarded pilgrimage and trade routes. At one time, the order controlled more than two dozen castles in the Middle East.

The fall of Acre (which the Knights Hospitaller defended), in 1291, is considered to be the end of the Crusades. At that time, the Knights Hospitaller moved their headquarters to Limassol, a city on the island of Cyprus.

The Knights Hospitaller added a navy to their arsenal, protecting Holy Land pilgrims who chose to go by ship. Not long after that, the Knights Hospitaller chose the island of Rhodes as the new headquarters; at this time, they also became known as the Knights of Rhodes.

Also in the 13th Century, Knights Hospitaller wore a scarlet surcoat or tunic when going into battle. In the 14th Century, after the dissolution of the Knights Templar, Pope Clement V gave land belonging to that order to the Knights Hospitaller. Some former Knights Templar joined the Knights Hospitaller.

Rhodes fell to Ottoman armies led by Suleiman the Magnificent in 1522, and the Knights Hospitaller had no headquarters for awhile. In 1530, Charles V, the Holy Roman Emperor, gave the Knights the island of Malta, which they used as a new base of operations. They withstood several more attacks but lost the island to the French leader Napoleon in 1798.

The Knights of Malta returned to their namesake island in 1802 but lost ownership again in 1814, after the end of the Napoleonic Wars, which resulted in Malta's being taken over by Great Britain.

In 1834, the Knights Hospitaller set up headquarters in Rome, where the organization can be found to this day, having long since given up any military role. The official name now is the Sovereign Military and Hospitaller Order of St. John of Jerusalem, of Rhodes, and of Malta.