"The blue water, smitten by many oars, might be seen foaming far and wide" wrote a medieval monk who watched a Viking fleet set sail. Above: Detail from the Bayeux Tapestry, which commemorates the ...

Vikings raided for status, loot, slaves, and provisions. The tack spar helped control the sail’s front corner. Oar-holes could be closed when under sail, sealing out water in heavy seas.

SAILOR:Okay. Go. NEIL OLIVER:'If there was no wind, the Viking boats could be powered by oars. But they really came into their own as sailing ships. Then they were able to travel much, much further.

They could cross the open oceans under sail and then switch to oars for lightning-fast hit-and-run attacks on undefended towns and monasteries. Far surpassing contemporary English or Frankish ...