This book examines the early Muslim conquests that started with the first caliph, Abu Bakr, and accelerated during the reign of the second caliph, Omar. During this time, the Sassanids were destroyed, the political and commercial order of Rome was turned upside down, and the ancient period came to an end. Iraq, a province belonging to the Persians and the capital city of Ctesiphon, was the first of the regions the Caliphate entered. This book explores in detail the history of the Islamic conquests in Iraq, how and why the Sassanid Empire fell, and the Islamization policies of the Rashidun Caliphate.