He had quieted one possible ally of the empire. He addressed himself next to another opponent who had shown that he could be terribly formidable. He made a truce with John Hunyadi for three years and concluded arrangements with the rulers of other states. He strengthened his army. He amassed stores of arms, arrows, and cannon-balls. He superintended the thorough reform of the administration of the revenue, and in the course of a year he accumulated a third of the taxes which would otherwise have been squandered. [Sidenote: Purposes building fort on Bosporus.] Then he determined to carry into execution a plan which would give him a strong base for operations against the city he was resolved to capture. He was already master of the Asiatic side of the Bosporus. At what is now Anatolia-Hissar he possessed the strong fortification built by Bajazed. It is at the place where Darius crossed from Asia into Europe and where the Bosporus is narrowest, being indeed only half a mile broad. Mahomet already possessed by treaty, made with his father, the right to cross the straits and to march through the peninsula behind Constantinople to his capital at Adrianople. He now, however, proposed to build another fortification at some point on the opposite--that is the European--shore. It would serve the double purpose of enabling him to command the straits and of giving him a base for obtaining his supplies from Asia and for the attack by sea upon the city. With a fleet already large at the Dardanelles and with the command of the Bosporus, he hoped to isolate Constantinople so far as to prevent it from receiving any aid in men or supplies of food. The command of the Bosporus would be a blow to the trade of Venice and Genoa as well as to the emperor. Ships would be prevented from trading freely with, and bringing supplies from, the Black Sea. It might have been expected that the emperor would have put forth all his strength to oppose the execution of such a design. The all-sufficient explanation is, that, even if his naval strength had been sufficient to delay the crossing of Mahomet’s crowd of builders, the army was too hopelessly insignificant to hold the shore against that which could soon arrive from Adrianople on its rear. [Sidenote: Remonstrances against project.]