Answer:
Muhammad's hegira from Mecca marks the beginning of a new polity. For the first time in Arabia members of a community were bound together not by the traditional ties of clan and tribe but by their shared belief in the one true God. Later believers, looking back on this event, recognized its seminal importance by designating it as the first year of their new era. In further recognition of this great event, the oasis of Yathrib came to be called Medina, "the city [of the Prophet]."
It gave them more power because before they didn't have much power.
Justinian I failed to regain all of the former provinces of the old Roman Empire really from a combination of all these reasons, but the main one was that he made military blunders.
The southern people wanted the slaves to be counted as state population because they wanted to have more votes in the south.
Muhammad is the prophet and founder of Islam. Born in Mecca in 570, most of his early life was spent as a merchant. At age 40, he began to have revelations from Allah that became the basis for the Koran and the foundation of Islam.
