Mehmed had taken the city of Constantinople just three years earlier, making the city his capital. Mehmed's supposed ally Đurađ Branković, the ruler of Serbia, was supposed to assist in the taking of Constantinople but had failed to do so. Branković also refused to pay tribute and so in 1454 the Ottomans invaded Serbia. Unable to swiftly subdue the country, Mehmed left Serbia to gather more troops, leaving behind a small force and instructions to avoid battle. The Ottoman's were unable to avoid a pitched battle and the Serbians where able to neutralize this force. In 1456 Mehmed again invaded Serbia, and quickly made their way to Belgrade. The Ottomans quickly put the town under siege and got through the first set of walls before being pushed back by the defenders. The next day a group of Serbian soldiers sallied out from the walls and began looting the Ottoman camp, cavalry was sent against them but in the confines of the camp they where not able to move and where pushed back. Seeing this more soldiers left the besieged city and began attacking the Ottomans. The Ottoman troops panicked and began fleeing and Mehmed moved in with his Janissaries to get control of the situation. Mehmed was wounded and forced to leave the battle, leaving the Serbians victorious.
What if Mehmed is killed in this engagement? Does the Ottoman Empire start crumbling before reaching its' potential? Not long after this battle the Ottomans would have to fight for control of Anatolia against the Aq Qoyunlu Confederation to the east? What do you think hapens to the Ottoman Empire and how does this change history for Europe and the middle East?