When the emperor and citizens learned, in the spring of 1452, the preparations which were being made by the collection of building materials and the bringing together of crowds of workmen, they recognised all the importance of the project and its danger to the city. Ambassadors were sent to the sultan at Adrianople to learn whether it was possible in any way to divert Mahomet from his purpose. They urged the existence of treaties with the grandfather, the father, and even with Mahomet himself: treaties which had expressly stipulated that no fortification or other building should be erected on the European side of the Bosporus.[201] They claimed that these stipulations had hitherto been scrupulously observed, that armies had been allowed to pass, but Mahomet’s predecessors had prevented any of their subjects putting up fortifications or other buildings. The messengers urged upon the sultan that to break the treaties was to commit an act of injustice to the emperor. [Sidenote: Mahomet’s reply.] In reply, the sultan, who was determined to avoid war till he was ready, declared to the messengers that he had no intention of breaking treaties: a statement which was, of course, in flagrant violation of the truth. He pointed out, however, that in the time of his father the Italians had tried to hinder the passage of his troops when it had become necessary to fight the Hungarians, and urged that it had become essential for the protection of his European possessions that he should be in a position to prevent such detention in future. He claimed that the land on which he proposed to build his fortress belonged to him, and professed to think it strange that the emperor should wish to place any difficulties in the way of the execution of so necessary a project. If indeed, he significantly added, the emperor was not peaceably disposed, that would be a different matter.[202] When the messengers reported their interview, the emperor’s first idea was to fight, and he was only prevented by the entreaties of the clergy and people from sending a detachment of his troops to destroy the builders and their work. Some indeed of the inhabitants were in favour of such action, but the emperor[203] had to come to the miserable conclusion that it was impossible to prevent the young sultan from carrying out his project except by war in the open country, and that for such war he was not prepared. [Sidenote: Selects a site at Roumelia-Hissar.] When the spring of 1452 was further advanced the sultan himself took the lead in the execution of his project. He assembled thirty well-armed triremes and a large number of transports and sent them from Gallipoli to the Bosporus. At the same time he himself marched at the head of a large army towards its European shore. On his arrival he selected, with the aid of his engineers, the most advantageous position for his proposed fortifications. This was found immediately opposite Anatolia Hissar.[204] [Sidenote: Building begins.]