In the last days of March Trevisano with his crew, aided also by Alexis (or Aloysius) Diedo, whose three galleys had come from Tana on the Azof, reopened a foss from the Golden Horn in front of the landward walls as far as the ground remained level, and at the same time repaired the walls in the neighbourhood.[211] A few days later the Italians were assigned to the most important positions on the landward walls. Barbaro, with the enthusiasm of a Crusader, gives a list of Venetian nobles who took part in the defences, and this ‘for a perpetual memorial’ of his brave countrymen. Justiniani appears at first to have chosen to defend the walls at Caligaria. [Sidenote: Closing the harbour.] On April 2 the chain or boom which defended the entrance to the Golden Horn was either closed for the first time or strengthened.[212] It extended from the Tower of Eugenius near Seraglio Point to the Tower of Galata,[213] within the Galata Walls, and near the present Moumhana, and was supported on logs. Ten large ships, of which five were Genoese, three from Crete, one from Ancona, and an imperial ship, were stationed at the boom, bows towards it, and with long triremes near them for support. The guardianship of the boom was entrusted to the Genoese.[214] By the end of March Mahomet’s preparations were nearly complete. He had already summoned all available cavalry and infantry from Asia and the parts of Europe under his control. As they arrived he drilled, classified, and formed them into bodies of cuirassiers (or men with breastplates), slingers, archers, and lancers. [Sidenote: The Turkish army.] While it is impossible to state with anything like certainty what was the number of fighting men whom Mahomet was shortly to bring before the walls of the city, the materials for forming a general computation are not wanting. The Turkish army was composed of regulars and irregulars. The first and most important division of regulars were the Janissaries. After them came a great horde of Turks from those who had occupied Asia Minor and Europe. Every Turk was bound to serve, and a call had been made on all. The Turkish nation was the Turkish army. Among them were many men who represented the class subsequently known as Derrybeys, chieftains who held their lands from the sultan on condition of bringing a number of retainers into the field during war. The irregulars, or, as they may be conveniently called, the Bashi-Bazouks, consisted partly of the poorest class of Turks, who did not possess a horse, and partly of Christians attracted by the hope of plunder.