1. At the time of his death in 632, Muhammad had not left any instructions regarding his succession, and he had only girls
2. His companions appointed Abu Bakr as Caliph (Khalifa, calife)
3. He tried to reinforced Muhammad's political work, since his death revealed its fragility
4. Several Arab tribes abjured Islam in 632 since they considered their conversion as a personal oath to Muhammad
5. When he died in 634, Islam had spread all over Arabia
6. It became conceptualized as the religion of the Arab people and gave them a unity factor
7. The Arabs were ready to expand, which they did under the reign of caliph Umar (r.634-644)
8. In 634, 2 armies were sent against Byzantine Syria and against Sasanian Iraq
9. Their generals were surprised by the easy victories
10. State of exhaustion of both the byzantine and Sasanian armies
11. Islamic armies were composed of hard men, galvanized by their new faith and its universal ambition
12. They were also attracted by easy booties
13. They were led by skilled generals, like Khalid B. Al-Walid, whose battleplans are still taught now in military schools
14. In 636, the Byzantine are vanquished and let the Islamic armies take Jerusalem and more widely, conquer Syria
15. The same year, the Sasanian (Persians) lost a key battle at Al-Qadisiyya, Leaving Iraq to the Arabs
16. In 640, Islamic armies conquered Egypt and launched their first raid toward the Maghrib
17. In the East, Muslims attacked Sasanians Iran, whose conquest put an end to the Sasanian Empire (654)