Answer:
After successful unification of Arabian tribes under Islam, Muslims have faced two threats: the Byzantines to the West and the Persians to the East. Both had technological advantages over the Muslims: Romans with elite armoured units, Persians with war elephants and several sophisticated army divisions, each with over 100,000 well equipped elite soldiers. To counter the numerical superiority of their armies, Muslims with there sacrificial nature and stronger will power were able to demoralise their infantries and also with impeccable mobility, accustomed to swift movement and hardship in the field, they have outclassed their heavily equipped attacks and movements.