The assassination of #AliIbnAbiTalib, the fourth & last of the #RashidunCaliphate, on #ThisDayInHistory in 661 led to creation of the #UmayyadDynasty, the first Arab-Muslim empire and monarchy. #Ali was killed by a #Kharijite, member of a radical sect that rejected the caliphate.

The #BattleOfAlQadisiyyah took place on #ThisDayInHistory in 636. Despite both sides taking heavy casualties, it was a decisive victory for the #RashidunCaliphate against the #Sasanid Persian Empire. It cleared the way for the whole of #Mesopotamia to fall, including #Ctesiphon.