The great snow of 627

In 627 snow lay several feet deep on level ground in the eastern steppe. The herds of the khaganate died in it.^[1] The people starved.^[1]

Effect on the herds

A steppe economy keeps its wealth in livestock, and the livestock lives outdoors. Deep snow with a crust puts the grass out of reach. Animals that cannot dig starve where they stand. Horses break the crust for the sheep, and when the horses die, the rest of the herd dies with them. A herd lost in one winter is not replaced in one summer. Someone has to feed the household that lost it.

The khaganate answered by taking from its subject peoples. A khan does this when his own herds are gone, and it costs him their loyalty.

Consequences

Töles was flogged by Ilig and then refused troops. In 629 he went over to the Tang.^[1] The Xueyantuo seceded and set up a khaganate of their own. The Zizhi tongjian dates this to 628, the Jiu Tang Shu to 629.^[2] The Tang had paid Ilig off at the Wei bridge the year before the snow. Now they waited and watched the reports.

In the winter of 629 Tang cavalry struck north. The khaganate that had stood before Chang’an three years earlier came apart without a great battle.^[1]

Place in the collapse

Modern accounts usually tell the collapse of the first khaganate as a political story. A khan mismanaged his subjects, and a Chinese court outplayed him. The annals put a winter in the middle of it. The record of climate places that winter in a run of cold years.

Neither account replaces the other. The snow did not make the Töles rebel. The taxation that followed the snow did, and the khan chose that. The winter removed the margin in which his choices could have been wrong without being fatal.