The companions of Mohammed lost no time in appointing his successor.  Their choice fell upon Abu-bekr, his friend and father-in-law, who was a person of an energetic character, brave, chaste, and temperate.  Abu-bekr proved himself quite equal to the difficulties of the situation.  Being unfit for war himself, as he was above sixty years of age, he employed able generals, and within a few months of his accession struck such a series of blows that rebellion collapsed everywhere, and in a short time the whole Arab nation, except the tribe of Gassan, acknowledged themselves his subjects.  Among the rivals against whom he measured himself, the most important was Moseilama.  Moseilama, who affected the prophetic character, had a numerous following, and was able to fight a pitched battle with the forces of Abu-bekr, which numbered 40,000 men.  At the first encounter he even succeeded in repulsing this considerable army, which lost 1200 warriors; but in a second engagement the Mohammedans were victorious—­Moseilama was slain—­and Kaled, “the Sword of God,” carried back to Medina the news of his own triumph, and the spoils of the defeated enemy.  Soon after the fall of Moseilama, the tribes still in rebellion submitted themselves, and the first of the Caliphs found himself at liberty to enter upon schemes of foreign conquest.

Distracted between the temptations offered to his arms by the East and by the West, Abu-bekr in his first year (A.D. 633) sent expeditions in both directions, against Syria, and against Hira, where Iyas, the Persian feudatory, who had succeeded Noman, son of Al Mondar, held his court, on the western branch of the Euphrates.  For this latter expedition the commander selected was the irresistible Kaled, who marched a body of 2000 men across the desert to the branch stream,s which he reached in about latitude 30 deg..  Assisted by Al Mothanna, chief of the Beni Sheiban, who had been a subject of Iyas, but had revolted and placed himself under the protection of Abu-bekr, Kaled rapidly reduced the kingdom of Hira, took successively Banikiya, Barasuilia, and El Lis, descended the river to the capital, and there fought an important battle with the combined Persian and Arab forces, the first trial of arms between the followers of Mohammed and those of Zoroaster.  The Persian force consisted entirely of horse, and was commanded by a general whom the Arab writers call Asadsubeh.  Their number is not mentioned, but was probably small.  Charged furiously by Al Mothanna, they immediately broke and fled; Hira was left with no other protection than its walls; and Iyas, yielding to necessity, made his submission to the conqueror, and consented to pay a tribute of 290,000 dirhems.