Regardless, the death of Yazdegerd marked the end of the Sasanian Empire, and made it less difficult for the Arabs to conquer the rest of Iran. All of Khorasan was soon conquered by the Arabs, who would use it as a base to attack Transoxiana. The death of Yazdegerd thus marked the end of the last pre-Islamic Iranian empire after more than 400 years of rule. An empire–which had a generation earlier briefly conquered Egypt and Asia Minor, even reaching as a far as Constantinople, fell to a force of lightly equipped Arabs that were used to skirmishes and desert warfare. The heavy Sasanian cavalry was too sluggish and systematized to contain them; employed light-armed Arab or East Iranian mercenaries from Khorasan and Transoxiana would have been much more successful.