The Knights Hospitaller of Saint John — formally the Sovereign Military Hospitaller Order of Saint John of Jerusalem — had been a crusading order since the early 12th century. They had been pushed out of the Holy Land at the 1291 fall of Acre, regrouped briefly on Cyprus, and in 1309 captured the Byzantine Aegean island of Rhodes from its Greek Orthodox population under the leadership of the Grand Master Foulques de Villaret.
They held the island for the next 213 years.
The fortified state
Rhodes under the Hospitallers was substantively a sovereign crusader state. The Order recognised no temporal lord above the Grand Master, struck its own coinage, maintained its own navy, levied its own taxes, and conducted its own foreign policy with the surrounding Byzantine, Mamluk, and Italian-mercantile powers. The institutional structure was a self-perpetuating aristocratic religious order with members drawn from the Catholic noble families of Western Europe; the Grand Master was elected for life by the senior chapter.
The substantial physical legacy of the period is the fortified Old Town of Rhodes — approximately 4 km of double-walled fortifications, eight bastioned gates, and the substantial Grand Master’s palace at the northern end. Most of what survives today was built during the long Grand Mastership of Pierre d’Aubusson (1476–1503), in direct response to the first major Ottoman attempt on the island in 1480. The 1480 siege, by Mehmed II’s forces, was beaten off after three months; d’Aubusson then spent two decades substantively upgrading the fortifications to the highest available European Renaissance military-engineering standard.
The Hospitallers also held parallel mainland positions on the Anatolian coast. The Castle of Saint Peter at Bodrum — built between 1402 and 1437 out of stone quarried from the ruins of the Mausoleum at Halicarnassus — was the principal Hospitaller mainland base. Both Rhodes and Bodrum operated under the substantive 1402 truce with the Ottoman beylik that had been negotiated after the Battle of Ankara.
The 1522 siege
Suleiman the Magnificent succeeded to the Ottoman sultanate in 1520. He moved decisively against Rhodes in summer 1522 with an army of perhaps 100,000 soldiers and 200 ships. The Hospitaller defence under Grand Master Philippe Villiers de l’Isle-Adam mustered approximately 7,500 defenders (700 knights and the remainder local Greek and Italian militia). The siege lasted six months.
The substantive critical fact was that no help came. The European Catholic powers — France, the Empire, the Italian states — were preoccupied with the Habsburg-Valois wars and declined to send relief forces. The Republic of Venice, which had commercial interests in the eastern Mediterranean, declined to break its own truce with the Ottomans. The Pope sent encouraging letters but no military force.
The defenders surrendered on terms in December 1522. Suleiman granted the surviving knights safe passage with their personal weapons and movable property; approximately 180 surviving Hospitallers boarded a small fleet and left Rhodes for the last time on 1 January 1523.
Malta
The Order spent the next seven years on a slow Mediterranean diplomatic search for a new sovereign base. In 1530 Charles V granted them the islands of Malta in feudal tenure for the nominal annual rent of one trained Maltese falcon. The Order substantively recreated the Rhodes institutional model at Malta and held the new island against a second Ottoman siege in 1565. Malta would remain their sovereign base until Napoleon’s 1798 capture of the island en route to Egypt.
The Rhodes fortifications substantively survive today. They are the most complete late-medieval European military-engineering complex still standing anywhere in the eastern Mediterranean.