As a result of heavy losses inflicted by the Ottomans in the Battle of Maritsa in 1371, the Serbian Empire had dissolved into several principalities. In the Battle of Kosovo in 1389, Serbian forces were again annihilated. Throughout the 15th and 16th centuries, constant struggles took place between various Serbian kingdoms and the Ottoman Empire. The turning point was the fall of Constantinople to the Turks. In 1459, following the siege, the temporary Serbian capital of Smederevo fell. Zeta was overrun by 1499. Belgrade was the last major Balkan city to endure Ottoman forces. Serbs, Hungarians, and European crusaders defeated the Turkish army in the siege of Belgrade in 1456. After repelling Ottoman attacks for over 70 years, Belgrade finally fell in 1521, along with the greater part of the Kingdom of Hungary. The rebellion of Serbian military commander Jovan Nenad between 1526 and 1528 led to the proclamation of the Second Serbian Empire in modern-day Serbian province of Vojvodina, which was among the last Serbian territories to resist the Ottomans. The Serbian Despotate fell in 1459, thus marking the two-century-long Ottoman conquest of Serbian principalities.