At Rhodes the knights reached the peak of power and influence, never quite attained in the same measure before or after. And this is all the more remarkable because the number of knights on the island never exceeded three hundred. By building enormous fortifications they made the island an almost impregnable bastion against the attacks of the Mamelukes of Egypt and Syria and the Turks of Constantinople. With their naval power they started a new type of warfare against the old enemies. In Rhodes the knights became a sovereign power like the sea republics of Italy or the Hanseatic cities in Germany.[11] Their navy flew its own flag, a white cross on a red field, they minted their own money, they concluded treaties with other sovereign states on the basis of equality and they had their diplomatic representatives at many courts. After repulsing numerous attacks, the knights finally were overwhelmed by a strong expeditionary force under Sultan Soliman I and capitulated Dec. 21, 1522. Once again the remaining knights drifted around in search of a dwelling place; they established their capital successively in Crete, Messina, Baia, Viterbo, and Nizza. Finally, on March 24, 1530, they obtained from Emperor Charles V, in his capacity as king of Sicily, the island of Malta and adjacent islands as a “perpetual and free feud.” The only obligation attached to this transfer was that the knights should annually, on the feast of All Saints, offer a falcon or a hawk to the King of Sicily, whoever he might be. Thus the Order of Saint John became a feudatory of the kingdom of Sicily territorially, but as a religious order it continued dependent on the authority of the Holy See. From their key position in the Mediterranean, the knights watched the movements of the Turkish fleet and engaged in battle the corsairs from Tripoli and the other Barbary States. Twice a year the order equipped a “caravan,” namely a naval expedition, to ferret out pirates along the coastline of the Mediterranean. As in Rhodes, in Malta the knights sustained several attacks from the Turks, the most memorable of which was the “Great Siege” (1565). The knights were victorious on all occasions. However, in the eighteenth century a decline in spirit and in discipline set in. What the Turks failed to achieve, Napoleon did; on his way to Egypt, without striking a blow he captured the fortress of Malta, believed to be impregnable (June 12, 1798). The weak Grand Master Ferdinand von Hompesch soon resigned and the order established a provisional headquarters at Trieste which at the time was under Austria.