It hit the entire Mediterranean basin, killing nearly half of the population, just during the period Justinian was trying to rebuild the old Empire. The effects were described in the recent book Justinian's Flea. Without it the Roman Empire might have been rebuilt and there likely would never have been a Muslim Conquest. Persia would still be Zoroastrian, Pakistan and Indonesia would still be all Hindu and Buddhist, the history of Western Europe would have been transformed beyond any recognition.
What might’ve had happened had Gen. Washington had the benefit of several mild winters? Or the dust bowl years not so dry? I wonder, I wonder.