In April 1443 King Vladislaus and his barons decided to mount a major campaign against the Ottoman Empire. With the mediation of Cardinal Cesarini, Vladislaus reached a truce with Frederick III of Germany, who had been the guardian of the child Ladislaus V. The armistice guaranteed that Frederick III would not attack Hungary in the subsequent twelve months.

Spending around 32,000 gold florins from his own treasury, Hunyadi hired more than 10,000 mercenaries. The King also mustered troops, and reinforcements arrived from Poland and Moldavia. The King and Hunyadi departed for the campaign at the head of an army of 25–27,000 men in the autumn of 1443. In theory, Vladislaus commanded the army, but the true leader of the campaign was Hunyadi. Despot Đurađ Branković joined them with a force of 8,000 men.

Hunyadi commanded the vanguards and routed four smaller Ottoman forces, hindering their unification. He captured Kruševac, Niš and Sofia. However, the Hungarian troops could not break through the passes of the Balkan Mountains towards Edirne. Cold weather and the lack of supplies forced the Christian troops to stop the campaign at Zlatitsa. After being victorious in the Battle of Kunovica, they returned to Belgrade in January and Buda in February 1444.