In the summer of the year 636, somewhere in the broken volcanic country south of the Yarmouk River, two armies collided with a force that would reshape the known world. One was the field army of the Byzantine Empire—heir to Rome, guardian of Christianity, possessor of the Mediterranean’s most formidable military tradition. The other was a coalition of Arab tribes recently unified by a new faith and led by a general whose name would become synonymous with tactical genius. The Byzantines outnumbered their opponents, out-equipped them, and held every conventional advantage that military theory of the age considered decisive. Within six days, they had been annihilated. Their emperor would retreat to Constantinople, never to return to the East. Their provinces would fall, one after another, to an expansion that within a century would stretch from the Atlantic to the Indus. And the battle that triggered this transformation—the Battle of Yarmouk—would become one of the most decisive engagements in the history of warfare.
This book is a study of that battle. It is also a study of what that battle can teach us about the wars we are fighting today, and the wars we will fight tomorrow.