Leadership and the spread of Islam

Leadership and the spread of Islam. How did the four caliphs utilize military and political and religious leadership to enhance the growth of Islam?
• Military Leadership in the Spread of Islam
• Military leadership and the spread of Islam (Campbell, 2008).
• Strategies and tactics used and Impact the Spread of Islam (Shah, 2006).
Abu Bakr: military campaigns and expansion to [put the regions]; suppressing apostasy wars;
Umar ibn al-Khattab: military campaigns and expansion to [put the regions];
Uthman: military campaigns and expansion to [put the regions];
Ali: internal conflicts; First Fitna (civil war)