The Ottoman Sultan, Mehmed II invaded Serbia in May 1454 and laid siege to Smederevo, thus violating the truce of November 1451 between his empire and Hungary. Hunyadi decided to intervene and started to assemble his armies at Belgrade, forcing the Sultan to lift the siege and leave Serbia in August. However, an Ottoman force of 32,000 strong continued to pillage Serbia up until Hunyadi routed them at Kruševac on 29 September. He made a raid against the Ottoman Empire and destroyed Vidin before returning to Belgrade.