In the century after the death of Osman I, Ottoman rule began to extend over the Eastern Mediterranean and the Balkans. Osman's son, Orhan, captured the city of Bursa in 1326 and made it the new capital of the Ottoman state. The fall of Bursa meant the loss of Byzantine control over Northwestern Anatolia. The important city of Thessaloniki was captured from the Venetians in 1387. The Ottoman victory at Kosovo in 1389 effectively marked the end of Serbian power in the region, paving the way for Ottoman expansion into Europe. The Battle of Nicopolis in 1396, widely regarded as the last large-scale crusade of the Middle Ages, failed to stop the advance of the victorious Ottoman Turks. With the extension of Turkish dominion into the Balkans, the strategic conquest of Constantinople became a crucial objective. The Empire controlled nearly all former Byzantine lands surrounding the city, but the Byzantines were temporarily relieved when Timur invaded Anatolia in the Battle of Ankara in 1402. He took Sultan Bayezid I as a prisoner. The capture of Bayezid I threw the Turks into disorder. The state fell into a civil war that lasted from 1402 to 1413, as Bayezid's sons fought over succession. It ended when Mehmed I emerged as the sultan and restored Ottoman power, bringing an end to the Interregnum.