The religion of Islam (and its official language, Arabic) began the unification of the tribes and city-states of the Arabian Peninsula into an expanding Islamic Empire.
The time period (661-750 CE) immediately following Muhammad's death, in which the new Islamic Empire was under control of the Umayyad clan. This was a time of rapid expansion and military conquest for Islam.
A series of religious and political wars launched by European Christians to reclaim Jerusalem and other holy sites from Muslims.