Pisan merchant ships as far back as 1052 had been trading to Egypt and the Levant, and in 1063 Ingulf, Abbot of Croyland in England, had returned from a pilgrimage in a Genoese merchant ship he had found at Jaffa. But it was not until the year 1090 that the conquest of Sicily was effected from the Mussulman hands, and thus the Straits of Messina became safe for shipping, and the vessels from Genoa and Pisa could go ahead in safety with their Levantine trade. By the twelfth century, Genoese, Venetian and Pisan seamen and merchants used to meet at Acre, to their great financial benefit, though not without manifestations of commercial jealousy. But we must dismiss from our minds all thoughts of single ships sailing across from Italy to the Syrian coast when they liked. There was hardly a time when there were not some pirates or corsairs hovering about; so the seas might be rid of one chief, but rendered dangerous by the rovings of another. Thus it was that shipowners had to do exactly what British mercantile owners were compelled to resort to in the latter part of the Great War, when the enemy was attacking so many of our trading craft—the convoy system had to be employed. Thus, from Venice, for instance, at regular intervals a convoy of merchant ships would sail for Acre, escorted by as many as thirty or forty galleys sometimes, as protection against piratical attack. If the Venice-Acre trade route were cut, it would mean that the French, the Germans, the Lombards, the Tuscans and other merchants would not receive the silks, sugar, pepper and other very valuable Oriental produce which the Venetians were bringing across in their ships. Thus the navy of Venice was charged with the duty of protecting its merchant fleet from the attacks of Genoese, Greek or Arab pirates. Just as during our recent war convoys used to collect at Falmouth and other ports prior to beginning their ocean voyage, so in the Middle Ages the convoy—called a _mudia_—would collect at Venice, bound for Syria or Egypt. There were only two convoys in the year, so the number of ships was large, and well needed the strong galley protection. One convoy left Venice in the spring and got back home in September; the other left in August, spent the winter abroad, and returned in the following May. In addition to these commercial convoys, there were also the pilgrim convoys to Palestine. Genoa sent one convoy a year to Syria and Egypt, but during the fourteenth century her ships were cruising in the Black Sea and harassing Venetian craft which had penetrated the Sea of Azov.