With the end of the half-century-long Crusader threat to their European frontier, Murad's son Mehmed II was free to lay siege to Constantinople in 1453.

In 1444, the Hungarian king, Władysław III of Poland, in breach of a ten-year truce that existed with the Ottoman Empire following the Peace of Szeged, launched a new crusade.

That year his army breached the Hexamilion wall and ravaged the Peloponnese after which, following the proclamation of a new crusade by Pope Nicholas V, Murad invaded Albania, conquering the fortress of Svetigrad.

[13] Meanwhile, four years after his defeat at Varna, John Hunyadi, the richest landowner in Hungary, had joined forces with Albania's war leader Skanderbeg in an alliance that also included Serbia and Bosnia.

[16][17] Hunyadi's strategy was based on an expected revolt of the Balkan peoples, a surprise attack, and the destruction of the main force of the Ottomans in a single battle after linking up with his allies.

[19] Believing the strength of his army to be inadequate to face the crusaders, Murad retreated back to Sofia to stockpile resources necessary for the campaign and receive reinforcements.

[20] While gathering the necessary provisions in Sofia, news reached the army that a Wallachian force had crossed the Danube and attacked Ottoman positions in Nicopolis.

[20] The POWs captured during the ambush were sent to Sofia, where the news of the victory had increased morale among the Ottoman troops before their march towards the crusader army.

[30][17] Sultan Murad personally commanded a large section of cannoneers and janissaries, while his son and would-be successor, 16-year-old Mehmed, who faced battle for the first time, led the Anatolian troops at the right wing.

Calculating that he would need more than 40,000 men to defeat the Ottomans, the Hungarian regent sought to join up with anti-Ottoman Albanian forces, possibly led by Skanderbeg.

Cavalry skirmishing on the flanks of the stockades during the first two days and a Crusader night-time attack using their wagons and guns against the Sultan's central position on the night of 18/19 October produced much bloodshed but no conclusive results.