accounts, 60–70,000 according to newer research) arrived at Belgrade. The siege began on July 4, 1456. Szilágyi could rely on a force of only 5,000–7,000 men in the castle. Mehmed set up his siege on the neck of the headland and started heavily bombarding the city's walls on June 29. He arrayed his men in three sections: The Rumelian corps had the majority of his 300 cannons, while his fleet of 200 river war vessels had the rest of them. The Rumelians were arrayed on the right wing and the Anatolian corps were arrayed on the left. In the middle were the personal guards of the Sultan, the Janissaries, and his command post. The Anatolian corps and the Janissaries were both heavy infantry troops. Mehmed posted his river vessels mainly to the northwest of the city to patrol the marshes and ensure that the fortress was not reinforced. They also kept an eye on the Sava river to the southwest to avoid the infantry from being outflanked by Hunyadi's army. The zone from the Danube eastwards was guarded by the Sipahi, the Sultan's feudal heavy cavalry corps, to avoid being outflanked on the right. When Hunyadi was informed of this, he was in the south of Hungary recruiting additional light cavalry troops for the army, with which he would intend to lift the siege. Although relatively few, his fellow nobles were willing to provide manpower, and the peasants were more than willing to do so. Friar John of Capistrano had been sent to Hungary by the Vatican both to preach against heretics and to preach a crusade against the Ottomans. Capistrano managed to raise a large, albeit poorly trained and equipped, peasant army, with which he advanced towards Belgrade. Capistrano and Hunyadi traveled together though commanding the army separately. Both of them had gathered around 40,000–50,000 troops altogether. The outnumbered defenders relied mainly on the strength of the formidable castle of Belgrade, which was at the time one of the best engineered in the Balkans. Belgrade had been designated as the capital of the Serbian Despotate by Stefan Lazarević 53 years prior. The fortress was designed in an elaborate form with three lines of defense: the inner castle with the palace, a huge upper town with the main military camps, four gates and a double wall, as well as the lower town with the cathedral in the urban center and