King Harald Hardrada of Norway, unable to conquer Denmark despite his raids, wants a decisive victory over Sweyn.

He eventually sets out from Norway with a great army and a fleet of around three hundred ships.

Sweyn has also prepared for the battle, which has been preassigned a time and place.

Sweyn does not appear at the agreed time, and Harald thus sends home his nonprofessional soldiers (bóndaherrin), which had made up half of his forces.

When the dismissed ships are out of reach, Sweyn's fleet finally appear, possibly also with three hundred ships.

The battle at Niså, fought on August 9, 1062, at Nissan river, Halland, Denmark (modern-day Sweden), results in great bloodshed as Harald defeats the Danes (seventy Danish ships are reportedly left "empty"), but many ships and men manage to escape, including Sweyn.

Harald, like most others in the early phase of the battle, actively uses his bow as an archer.