That the Ottoman navy during most of the sixteenth and much of the seventeenth century had clear dominance of the eastern Mediterranean was through possession of the surrounding coastline and many of the islands in that region. This provided the galley squadrons of the Ottoman navy with an endless choice of local ports, so negating the normal disadvantage of the galley, that of having a reach restricted by the availability of friendly replenishing ports. Conversely, enemy galleys were prevented from carrying out plundering raids within the greater part of this region through their own lack of a supply port that would permit the taking on of water and other supplies. This dominance primarily took effect from around 1517 when the coastline surrounding the eastern Mediterranean came fully into the possession of the Ottomans, a result of the successful conquest of Egypt and the Levant, territories previously held by the Mamluk sultanate. In turn, most of the islands in the eastern bay of the Mediterranean, and not already in possession of the Ottomans, were captured, with Rhodes falling into their hands in 1523. This was an important acquisition, the island having been used by the Knights Hospitallers of the Order of St John in a long drawn out sea war against the Ottomans legitimised under the concept of a perpetual crusade. The Knights, a corporately financed international force with a small but highly efficient navy, through possession of Rhodes had been a danger to all Ottoman ships entering the Mediterranean. In 1570, Cyprus had also been successfully captured, but an attempt to conquer Malta in 1565, the new home of the Knights of St John, failed after a four-month siege. While the taking of Rhodes and Cyprus had been made possible through their proximity to existing Ottoman territory, and so within easy range of a galley fleet carrying an invading military force, Malta proved more difficult, as, in lying outside the protected eastern bay of the Mediterranean, it was also much closer to enemy ports from which a counter-expedition under the auspices of the Papacy could be mounted.