The first recorded use of this mounted force was during the Siege of Damascus (634). The best use of this lightly armed fast moving cavalry was revealed during the Battle of Yarmuk (636 AD) in which Khalid ibn Walid, knowing the importance and ability of his cavalry, used them to turn the course of events at every critical instance of the battle. With their ability to engage and disengage, and turn back and attack again from the flank or rear, the Mobile Guard inflicted a shattering defeat of the Byzantine army. This strong mobile striking force was often used in later years as an advance guard. It could rout opposing armies with its greater mobility that gave it an upper hand against any Byzantine army. One of the victories of the mobile guard was at Battle of Hazir in 637 CE under the command of Khalid, in which not a single Byzantine soldier survived. With this mobile striking force the Muslims easily conquered Syria with few casualties, including the Muslim victory at Battle of Iron Bridge which followed the surrender of Antioch.