The basic strategy of early Muslim armies setting out to conquer foreign land was to exploit every possible drawback of the enemy army in order to achieve victory with minimum losses as the Rashidun army, quality-wise and strength-wise, was sub-standard to the Sassanid Persian army and the Byzantine army. Khalid ibn Walid, the first Muslim general of the Rashidun Caliphate to conduct a conquest in foreign land, during his campaign against the Sassanid Persian Empire ("Iraq 633 - 634") and Byzantine Empire ("Syria 634 - 638") developed brilliant tactics that he used effectively against both the Sassanid army and the Byzantine army. The main drawback of the armies of Sassanid Persian Empire and the Eastern Roman Empire was their lack of mobility. Khalid ibn Walid decided to use the mobility of his own army to exploit the lack thereof in the Sassanid army and Byzantine army. Later the same strategy was adopted by all other Muslim generals throughout the period of military expansion. Though only part of the Rashidun army was actual cavalry, the entire army was camel mounted for movement. Khalid ibn Walid and then later Muslim generals were also able to make use of the fine fighting quality of the Muslim soldiers, the bulk of whom were bedouins and adept in swordsmanship.