But as we'll see, this division becomes stronger and stronger and stronger as there's more and more bloodshed between the two parties. Because so much of this revolves around the family of Muhammad, let's just review that first and then we'll talk about the division over who should succeed Muhammad as caliph or successor to lead the Muslim community. So you see Muhammad right over here, born 570. We have his birth on our timeline as well. And just to read this timeline, it goes from light blue to dark blue when Muhammad, according to Islamic tradition, starts to have the revelations from God. And the Muslim calendar starts at 622, the time of the Hegira, where the Muslim community, in order to escape persecution from the Quraysh, migrate from Mecca to Medina. Now we've talked about several of these figures in other videos.