Abu Bakrs Military Expeditions

A large number of the Prophet's Companions had been martyred in the Tabuk Battle.In order to retaliate the death of those martyrs the Holy Prophet had deputed Hadrat Zaid bin Harith's 17 years old brave son,Hadrat Usama,to Syria with the command of the unit of the Muslim army.But owing to Prophet's sickness and death Hadrat Usama and his detachment had to return to Madina.Immediately after assumption of office Caliph Abu Bakr deputed Hadrat Usama again to Syria to fulfill Prophet's interrupted mission without further delay.Hadrat Usama soon returned home after successful completion of the Syrian military expedition.The Caliph then set out in person at the command of the Muslim army to crush various internal uprisings with an iron hand.
    During those days the Arabian peninsula used to be surrounded by the two most powerful empires of the time:(1) the great Persian empire situated towards the east,and (2) the equally powerful Roman(or Byzantine) empire located on the     west.Both of these super powers had earned a great name and fame.But oppression and cruelty to the poor people and popularity of idolatry and polytheism had gone too far in both these empires.The Holy Prophet had once addressed a letter to Khusro Pervaiz,the emperor of Persia,inviting him to accept Islam.That short-sighted ruler had,however,torn the letter to pieces.In a fit of frenzy he had even ordered the arrest of the Holy Prophet.Similarly the Roman empire had also become the centre of all sorts of ills and evils.Syria used to be a part of the Roman empire those days.