Finally on 15 August, the Battle of Yarmouk was fought, it lasted for 6 days and ended in a devastating defeat for the Byzantines. The Battle of Yarmouk is considered to be one of the most decisive battles of history. It was the historic defeat that sealed the fate of Byzantines, the magnitude of defeat was so intense that Byzantine could never recover from it. It left whole of the Byzantine Empire vulnerable to the Muslims. The battle was the greatest battle ever fought on Syrian soil till then and was a tactical marvel of Abu Ubaidah.