The Siege of Belgrade: Rivers, Fortifications, and the Postwar Crisis

Belgrade controlled the confluence of the Danube and the Sava. Raids launched from there threatened Ottoman communications and supplies. Sultan Mehmed II resolved to capture the city and, in the winter of 1455–1456, began assembling artillery, provisions, livestock, and mills and ovens to accompany his army.

The defenders did not constitute a force drawn from a single source. János Hunyadi and the Hungarian nobility organized troops, while the Franciscan friar John of Capistrano recruited crusaders through his preaching; the Serbian despot George Branković also provided assistance. Military organization, aristocratic connections, and religious mobilization together sustained the defense.

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Capistrano arrived in Hungary in 1455, initially pursuing both religious reform and action against the Ottomans. After February 1456, he devoted most of his energies to the crusade. Catholics and Orthodox Christians were in conflict in the frontier region; fighting together did not mean these differences had disappeared. Capistrano had previously called for the suppression of Orthodoxy and promoted conversion, but the Hungarian nobles had not generally adopted his harsh proposals. Cooperation with the Orthodox Serbian ruler particularly involved practical political considerations. The friar’s exhortations also brought many poorly equipped rural inhabitants onto the battlefield.

On its landward side, the fortress had double walls and a deep ditch. Ottoman bombardment breached the walls, and the defenders filled the gaps with stones, earth, and timber. They also dug new ditches further inside, reconfiguring their defenses during the fighting.

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The blockade of the waterways threatened outside assistance to the fortress. Hunyadi’s flotilla forced the Ottoman fleet to yield the river passage, breaking the blockade before the decisive battle on land.

In his letter of July 23 to Szécsi, the archbishop of Esztergom, Hunyadi reported that the enemy had launched an assault on the evening of July 21. Fighting continued throughout the night and until noon on July 22. The defenders fought twice inside the city, then sallied out of the fortress and continued fighting until evening. His letter of the following day to Garai, the palatine of Hungary, preserved essentially the same account.

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These two early reports described the Ottoman retreat, the defenders’ capture of artillery, and the burning of ships, while acknowledging wounded and dead among their own men. Hunyadi repeatedly emphasized the severe damage to the fortress, even expressing uncertainty about what to do next. Once the besiegers had been driven off, restoring its defensive capacity remained an urgent task for the garrison.

The victors’ reports also served to mobilize support: Hunyadi depicted the enemy’s losses as exceptionally heavy to encourage a continued offensive. Latin and Ottoman accounts also differ over the fighting outside the walls, with the latter recording local successes by the sultan in defending his camp. The withdrawal can be established, but claims about enemy forces destroyed in the reports cannot simply be treated as troop statistics.

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As news of the victory spread, disease appeared in Belgrade and in the crusader camp across the river at Zemun. Hunyadi died on August 11; in a letter to the pope on August 17, Capistrano explicitly attributed his death to plague. By late summer, the crusaders had dispersed, weakening the manpower and leadership needed to build on the victory.

Comparing letters and chronicles, Igor Stamenović has shown that accounts celebrating victory and holiness often played down the epidemic, attributing deaths to exhaustion or vaguely defined illness. The dispersal of the troops may have aided transmission, but the surviving records are insufficient to calculate the total number of civilian deaths in the city or to attribute the epidemic throughout East-Central Europe to this campaign.

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Venice did not participate directly in the fighting but closely followed the reports. Its peace agreement with the Ottomans in 1454 and its interest in maintaining eastern trade made the republic reluctant to enter a war before a dependable alliance had formed. On August 12, 1456, the Senate sent its secretary, Pietro de Thomasiis, to Hungary, both to offer congratulations and to investigate local preparations and political developments in secret.

The envoy’s mission subsequently became one of offering condolences to Hunyadi’s family. When the Senate answered the Hungarian king’s envoys on October 23, it already referred to Hunyadi’s death and the dispersal of the Christian army. The defense of Belgrade had prevented the city’s capture in this campaign and won widespread acclaim. Yet disease, the army’s dissolution, and the states’ concerns over trade and security meant that victory did not automatically lead to a joint follow-up expedition. Venice also feared the effects of expanding Hungarian power on Dalmatia; the allies did not share the same expectations for the postwar settlement.

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