Final answer:
The spread of Islam in present-day Iraq is largely due to the military conquests and cultural integration under the Umayyad and Abbasid Caliphates, with Baghdad becoming a significant center for trade and Islamic scholarship. The support from local populations, particularly Persians, and the region's strategic location also played key roles.
Step-by-step explanation:
The dominance of Islam in the area that is present-day Iraq can be largely attributed to the expansion of the Islamic Caliphate after the death of the Prophet Muhammad in 632 CE.
The Muslims, under successive caliphates, notably the Umayyad and Abbasid dynasties, rapidly expanded their empire beyond the Arabian Peninsula to include regions such as the Middle East, North Africa, and Persia.
This expansion was achieved through a combination of military conquest and the establishment of Islamic governance and cultural practices, which led to Islam becoming the dominant religion in the conquered territories, including Iraq.
The Abbasids, who came to power in 750 CE, chose Baghdad in Iraq as their capital, and the city became a prominent center of trade, culture, and intellectual life. The Abbasid Caliphate facilitated the spread of Islamic civilization through trade, the Arabic language, and the spread of Islamic scholarship.
Notably, tribal groups and local populations, such as the Persians, who once made up the former Persian Empire, supported the Abbasids and were integral in the establishment and maintenance of the Islamic rule in the region.