One of the swords found in the Viking graves on the island of Sollerön in Sweden has a name engraved on it, Ulfberht. It was found in the first grave to be discovered. The temptation is to assume that this was the name of the Viking chieftain whose remains was buried there. Actually, the name is probably the first international “brand name”, ever.

The popular image of a Viking is that of a man with a sword and shield, but in fact, this is far from the truth. Reliable swords were very, very...