In 1396, apparently immediately after the battle of Nicopolis, and as an essential step towards the capture of the city, he built on the Bosporus the castle still remaining at Anatolia-Hissar, about six miles from the city. It served at once, and continued to serve until 1453, as a useful base of operations. After having completed it, says Chalcondylas, he went to besiege Byzance, and summoned Manuel to surrender the city.[115] The emperor, who had just welcomed six hundred French knights, sent by Charles the Sixth of France, did not deign to reply. Two years later, in 1398, in order to avoid an attack by the Turks, who were drawing near the capital with an army numbering ten thousand, nominally to support John, Manuel consented, as we have seen, to share the throne with his nephew, and thereupon went to Western Europe to endeavour to secure help. The aid sent to Sigismund from the West and that now sent to the Bosporus under Boucicaut show that many statesmen had awakened to the need of checking Turkish progress. The empire was able for a while to hold its own against the attacks made by the sultan. Bajazed, whose life was alternately one of great activity in warfare and of indescribable debauchery in the intervals between his campaigns, had kept the capital under terror of sieges during six weary years. In 1402, he summoned John to surrender the city, and swore by God and the Prophet that if he refused he would not leave in it a soul alive. John gave a refusal. Chateaumorand, the lieutenant of Boucicaut, who, as we have seen, had gone west to endeavour to obtain aid, took charge of the defence, and waited for an attack.