Bursa (from the Greek "Prusa") became the first major capital city of the early Ottoman Empire following its capture from the Byzantines in 1326. As a result, the city witnessed a considerable amount of urban growth throughout the 14th century. After conquering Edirne (Adrianople) in East Thrace, the Ottomans turned it into the new capital city in 1363, but Bursa retained its spiritual and commercial importance in the Ottoman Empire. The Ottoman sultan Bayezid I built the Bayezid Külliyesi (Bayezid I theological complex) in Bursa between 1390 and 1395 and the Ulu Cami (Grand Mosque) between 1396 and 1400. After Bayezid was defeated in the Battle of Ankara by the forces Timur in 1402, the latter's grandson, Muhammad Sultan Mirza, had the city pillaged and burned. Despite this, Bursa remained to be the most important administrative and commercial centre in the empire until Mehmed II conquered Constantinople in 1453. The population of Bursa was 45,000 in 1487.