In 1427, Stefan's successor Đurađ Branković had to return Belgrade to the Hungarian king, and Smederevo became the new capital. Although the Ottomans captured most of the Serbian Despotate, Nándorfehérvár – as it was known in the Kingdom of Hungary – was unsuccessfully besieged in 1440 and again in 1456. As it presented an obstacle to their advance into Hungary and further Europe, over 100,000 Ottoman soldiers launched the 1456 Siege of Nándorfehérvár, in which the Christian army under commander John Hunyadi successfully defended the city from the Ottomans, wounding Sultan Mehmed II. The "noon bell" ordered by Pope Callixtus III commemorates the victory throughout the Christian world to this day.