History -- 74 History 19 Islamic Empire -- 16 Caliphs 15 Islam 8 Caliphate 7 Caliphs -- 6 more ... Islam -- 6 Biography 5 Religious aspects -- 4 Islamic Empire 3 Politics and government 3 Biography -- 2 Dissertations, Academic 2 Historiography -- 2 Islam and politics -- 2 Leadership -- 2 Muslim women -- 2 Riddah Wars 2 Siffin, Battle of, Syria, 657 2 War -- 2 Abbasids 1 Apostasy -- 1 Arabic literature 1 Arabs -- 1 Caliphate -- 1 Camel, Battle of the, Iraq, 656 1 Circassians -- 1 Conduct of life 1 Dissertations 1 less ...