In one of our previous videos, we covered the battle of Yarmouk between the Byzantine Empire and the Islamic Rashidun Caliphate. This battle largely defined the fate of Eastern Mediterranean, but to the East, Caliphate had another global power to contend with - the Sassanid Empire. Two empires fought each other for more than 20 years, across dozens of battles with the campaign of the Muslim general Khalid ibn al-Walid in 633 and the battle of al-Qadissiyah that took place in 636 being the most crucial among them.