<P> The disintegration of the Seljuk Turks led to the rise of the Ottoman Turks . Their first important leader was Osman I Bey, who attracted Ghazi warriors and carved out a domain in north - western Asia Minor . Attempts by the Byzantine Emperors to drive back the Ottomans were unsuccessful, and ceased in 1329 with the Battle of Pelekanon . Following a number of civil disputes in the Byzantine Empire, the Ottomans subjugated the Byzantines as vassals in the late 14th century and attempts to relieve this vassal status culminated in the Fall of Constantinople in 1453 . </P> <P> The Byzantine Empire's survival depended upon its administration and the logistics that enabled it to run the Empire . Though considered complex, its system was one more advanced than those practised by the Frankish Kingdoms in the West and one modelled by the Islamic Powers of the East . As the Empire evolved into an increasingly smaller and defensive state, the governing of the state changed as well . However, by the 14th century the burdens of running an Empire surrounded by many enemies became too much of a strain on Byzantium's increasingly smaller resources . By c. 1350's, the Byzantines lost Thrace to the Ottomans; thereafter Constantinople became the government's primary administrative region . </P> <P> The Byzantine Empire experienced numerous civil wars . The defeats in the 7th and 12th centuries to the Arabs and Turks respectively speaking were in no small part assisted by numerous internal conflicts . The situation became worse later in the 14th and 15th centuries where Byzantine Emperors were forced to fight their own grandchildren / children, as in the cases of Andronikus II and Andronikus III . </P> <P> The Military of the Byzantine Empire was often smaller than that of its opponents and thus relied more upon strategy rather than brute strength to achieve success . This was in part achieved by the logistics of the Byzantine administration which allowed it to utilize their troops as efficiently as possible . Taxes on the peasantry were collected at times of need so as to raise the supplies needed at the time . However, this bureaucratic system was exploited by the social elite whose increasing power challenged that of the Emperor . Whilst the Theme system worked well to provide efficient military service, it led to the decentralization of power leading to disastrous civil conflicts in the 11th century . </P>

List three reasons for the final decline of the byzantine empire