The siege of Emesa in 638 was laid by a coalition force of Arab Christian tribes from Jazira which was mustered by Heraclius in an attempt to stem the losses of Byzantine territories due to the rapid expansion of the Rashidun Caliphate in the Levant.
HistoryLayer draws the world as it was in any year from 123,000 BCE to
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carries 23,890 events, 12,790 people, 837 wars and 13,183 cities, each
one readable in place. Signing in is optional and lets you keep what
you find.