Second, in large part because technology had accumulated, agrarian empires now had effective guns, allowing the Romanovs and Qing to close the steppe highway. Consequently, when social development pressed against the hard ceiling in the seventeenth century, the fifth horseman of the apocalypse—migration—did not ride. It was a struggle, but the cores managed to cope with the other four horsemen and averted collapse. Without this change, the eighteenth century might have been as disastrous as the third and thirteenth.
