The Norsemen had up to the middle of the eighth century played no part in the world's history. Their very existence had been unknown or but vaguely known to the rest of Europe. But towards the close of the eighth century they broke like a destructive tempest over the civilized lands, spreading desolation in their path. When their fast-sailing ships with two square sails were sighted at the river-mouths, people fled in terror, and the priests prayed in vain: "Deliver us, O Lord, from the rage of the Norsemen."