Battle of Yarmouk

Between August 15-20, 636, the Battle of Yarmuk took place. A Muslim army defeated the Byzantines. An excerpt from the article:

"The Battle of Yarmouk River (or Yarmuk River; also written as the Battle of Jabiya-Yarmuk) was fought over the course of six days, from 15 to 20 August 636 CE, between the Muslim army of the Rashidun Caliphate (632-661 CE), under Khalid ibn al-Walid (d. 642 CE) and the Byzantine legions, under field commander Vahan of Armenia (d. 636 CE). Fighting took place near the Yarmouk River in the Jordan valley, and the battle was a decisive victory for the heavily outnumbered Rashidun army. This victory permanently shifted the dominion in the Levant and Syria from the Byzantine Empire to the Caliphate. Moreover, this was the magnum opus of Khalid, who has been immortalized in legends for his triumph."