1. Political vacuum in Middle East left by collapse of Abbasid Empire filled only for short time by Seljuk Empire of Baghdad. Replaced by Mongol Ilhanid Empire (Tabriz) in Iran and Irak (capture of Baghdad in 1258) , Crusaders in Palestine and Syria, replaced by Ayyubid Empire of Saladin. Their quick collapse led to rise of Islamic military empires: Mamluk Empire of Egypt and Syria and Ottoman Empire of Anatolia and Southeastern Europe in late 13th, early 14th century.

2. Anatolia in the 13th century. Ottomans, one of many Turkoman principalities in Anatolia, rule Bithynia in northeast. Why able to defeat Turkomans and  ultimately take over Southeastern Europe and Anatolia?

3. Situation in 13th century Anatolia. East Roman Empire of Byzantines with capital in Constantinople (Istanbul). Armenian state around Lake Van and in caucasus, Georgians to north in Caucasus. Invasion of Turkoman nomads in 11th century through Cilician gates (Little Armenia)  after Great Seljuks of Baghdad unable to push them into Egypt against Fatimids. Turkomans conquer Anatolia, establish principalities, with Byzantines remaining only in western Anatolia and Trabzon on Black Sea. Seljuks of Rum establish state based at Konya, modeled after Great Seljuks. Defeat Byzantines at Battle of Manzikert (1071). Turkoman nomads as gazis, fighting infidel Christian Byzantines, Armenians and Georgians along frontiers of Anatolia. Anatolia becomes Turkish homeland, with Christians and Jews as tolerated minorities. Importance of Turkoman attachment to mystic orders (tariqa). Christian and mystic influence in developing Turkish culture. Importance of mystic orders in maintaining society in age of anarchy.

4. Ottoman origins. Myths about Ottoman ancestors: Suleyman ?ah leads Kay? Turkic tribe in Central Asia fleeing from Mongols through Iran, drowned in Euphrates River. Son Ertu?rul leads some members of family into Anatolia into service of Seljuks of Rum. Command gazis along western frontier against Byzantines in Bithynia.

5. Reasons for Ottoman success.

a. Geographic location. In best position to take advantage of Byzantine weakness, get more booty, so attract more Turkoman nomads entering Anatolia in flight from Mongols. Location along major trade route through Anatolia, able to levy protection taxes on caravans. Further away from Ilhanid Mongols of Tabriz, able to evade Mongol control.
b. Connection with mystic orders, who encourage nomads to enter Ottoman service as means of restoring order in Anatolia.