The Long Sword had a straight blade with two cutting edges and a one-handed hilt with a lobed pommel. The blade had deep fullers running the length of the blade to lighten it. The weapon was about three feet long, although later swords were longer.
The Long Sword was capable of thrusting and slashing. Due to the relative shortness of the hilt, it was almost always used one-handed, wielded with either a shield, axe or another sword. These swords would later evolve into the Norman Broadsword.
In the show it was tested against the Naginata, and was given the edge. While the Samurai won by a thin margin on the whole, the Viking's sword was deadlier than any other weapon used by the Samurai or Viking.