The Syrian war, the 21st century's most protracted and second-deadliest conflict, has driven 5.6 million refugees and 6.6 million internally displaced into flight. As the civil war draws to a close, an autopsy of this historic and unprecedented refugee episode becomes feasible. Why did the war generate so many refugees? How did so many of them get to Europe? Who are these people, and why did they leave? From whom were they fleeing and why? Did...