After the fall of Constantinople in 1453, Ottoman sultan Mehmed II is rallying his resources in order to subjugate the Kingdom of Hungary.

His immediate objective is the border fort (Hungarian végvár) of the town of Belgrade (in old Hungarian Nándorfehérvár).

John Hunyadi, a Hungarian nobleman and warlord of Wallachian and Hungarian lineage, who has fought many battles against the Ottomans in the previous two decades, expects just such an attack.

The siege eventually escalates into a major battle, during which Hunyadi leads a sudden counterattack that overruns the Turkish camp, ultimately compelling the wounded Sultan Mehmet II to lift the siege and retreat.

The noon bell ordered by Pope Callixtus III commemorates the victory throughout the Christian world to this day.