Space Viking by H. Beam Piper

This is the story of revenge and political intrigue against the sweep of a burgeoning Galactic Empire. Rising from the ashes of the "Old Empire" are the Space Vikings, people who are centered around the "Sword Worlds". Against this backdrop is the private war of Prince Lucas Trask and Andray Dunnan, a pretender to the throne of Gram. Dunnan set this war off by murdering Trask's wife on their wedding day at which point Trask equipped the ship he named "Nemesis" to go after Dunnan. The worlds and politics are drawn from the Viking era of our own past as well as WWII. The burning question is, does Prince Trask achieve his vengeance? What side results occur from his private war? All I can say is read the book and find out. Space Viking is currently out of print, so you'll have to hunt to find it, but I guarantee it's worth the effort!