It should be noted that contemporary non-Muslim accounts further validate the facts of the conquests. The writings of the Christian bishop of Jerusalem Sophronius (d.638), for instance, or the chronicles of the Byzantine historian Theophanes (d.758), to name a couple, make clear that Muslims conquered much of what is today called the “Muslim world.”
According to the Muslim historical tradition, the majority of non-Muslim peoples of the Old World, not desiring to submit to Islam or its laws (Sharia), fought back, though most were eventually defeated and subsumed.
The first major conquest, renowned for its brutality, occurred in Arabia itself, immediately after Muhammad’s death in 632. Many tribes which had only nominally accepted Islam’s authority, upon Muhammad’s death, figured they could break away; however, Muhammad’s successor and first caliph, or successor, Abu Bakr, would have none of that, and proclaimed a jihad against these apostates, known in Arabic as the “Ridda Wars” (or Apostasy Wars). According to the aforementioned historians, tens of thousands of Arabs were put to the sword until their tribes re-submitted to Islam. [PARALLELS TO THE AMERICAN CIVIL WAR]
The Ridda Wars ended around 634. To keep the Arab Muslims from quarreling, the next caliph, Omar, launched the Muslim conquests: Syria was conquered around 636, Egypt 641, Mesopotamia and the Persian Empire, 650. By the early 8th century, all of north Africa and Spain to the west, and the lands of central Asia and India to the east, were also brought under Islamic suzerainty.