Excerpts from Books and Wikipedia
"The Siege of Bursa (also called Prusa, Prousa, Brusa or Broussa) occurred from 1317/20 until the capture on 6 April 1326, when the Ottomans deployed a bold plan to seize Prusa (modern-day Bursa, Turkey). The Ottomans had not captured a city before; the lack of expertise and adequate siege equipment at this stage of the war meant that the city fell only after six or nine years. According to some sources Osman I died of natural causes just before the fall of the city, while others suggest that he lived long enough to hear about the victory on his death-bed and was buried in Bursa afterwards. After the fall of the city, his son and successor Orhan made Bursa the first official Ottoman capital and it remained so until 1366, when Edirne became the new capital. As a result, Bursa holds a special place in Ottoman history as their founding city, and also as the birthplace of Ottoman architecture (Bursa Grand Mosque (1399), Bayezid I Mosque (1395), Hüdavendigar Mosque (1385), and Yeşil Mosque) (1421)." [Wikipedia]