Genghis Khan's Secret Weapon Was Rain
Tree-ring studies suggest that a long wet spell gave him the resources to invade and conquer.
For unsuspecting herdsmen in the 13th century, April showers didn't bring May flowers—they brought Mongol hordes.
By sampling tree rings in the gnarled and twisted Siberian pines in the Hangay Mountains in central Mongolia, the team pieced together a remarkably precise chronology of local climatic conditions stretching from the year 900 A.D. to the present. The study, published in this week's Proceedings of the National Academy of Sciences, offers a new interpretation of why the Mongols suddenly went on the move.
The traditional view has been that the Mongols were desperately fleeing harsh conditions in their craggy, mountainous homeland. The Lamont-Doherty team, however, found just the opposite: Between 1211 and 1225—a period that neatly coincides with the rise of Genghis