The American Library in Paris

Ottomans are connected to the Kayı clan from Oğuzlar. In the time of the sultan of the  great seljuq empire Alaaddin Keykubat, Ottomans were placed three different place as a named Karacadağ, Söğüt and Domaniç. After the Kösedağ War, Kayı clan connected to the Ilkhanid Empire who occupied the Anatolia. Becoming a weak empire, Ilkhanid Empire faced a big problem; Osman Bey declare his independence. (1299) There were not any political unity in the balkans when the Ottoman clan was established. Kingdom of the serbian was the strongest empire in the balkans. Apart from that, there were Bulgarian, Hungarian and Albanian Empires , Wallachia, Moldavia, Bosnia, Herzegovina and Ardeal seigniory. The Ottoman clan has the geographical location that allows to extend. Also they constitute a strong central authority. Addition to that, there was not any political unity in the balkans. Thus these reasons and more, Ottomans enlarged really fast and easy.