But one thing is for sure in later tang dynasty, because of the rise of the Ottoman empire and other reasons, "land silk road" of the status began to weaken.

但有一点可以确定的是唐代中后期，由于土耳其帝国的突起等原因，“陆上丝绸之路”的位置开端减弱。

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The Ottoman dynasty did not observe primogeniture (the right of the first-born son to the throne), so in principle the throne was available to any imperial son.

BBC: Uncover the secrets of Topkapi Palace