Harald Hardrada, the 11th-century Norse adventurer of Don Hollway’s “The Last Viking,” led an iron-hammered life of struggle, travel, scheming and violence. Especially that last. As Tom Shippey observed in his history of Viking culture, “Laughing Shall I Die,” everything the ax-wielding warriors of the North did “was based on violence. That is what Vikings were good at, especially good at, spectacularly good at.”

And none more so than Harald Hardrada, Harald the Hard-Ruler or Tyrant, whose marauding ways came to an end in England at the Battle of Stamford Bridge, near York, in the pivotal year of 1066. In effect, the 51-year-old invader, by then the king of Norway, was caught by surprise. The Anglo-Saxon King Harold Godwinson unexpectedly quick-marched his army north, covering 200 miles in four or five days instead of the usual two weeks. Hollway calls this “one of the greatest feats of military tactics in medieval history.” Yet even though Harald, the “thunderbolt of the North,” was defeated and killed, he unknowingly exacted a cold revenge. Immediately after this costly, hard-fought victory, the Anglo-Saxon king and his remaining, exhausted troops were compelled to hurry back south to face William of Normandy — soon to be William the Conqueror — at the Battle of Hastings. A fresher, bigger army might have changed English history. As it was, in just three weeks both the age of the Vikings and the reign of the Anglo-Saxons reached a blood-drenched close.

When we think of Vikings, we generally picture dragon ships raiding the coasts of England and Scotland or intrepidly sailing westward across the Atlantic to Iceland and, quite probably, North America. Yet Harald passed much of his young manhood in the wild, wild East, where this “almost legendary Norse hero”— as John Julius Norwich calls him in “Byzantium: The Apogee”— served as a mercenary in the Byzantine Empire’s elite Varangian Guard, eventually becoming its de facto commander. He also participated in diplomatic missions and military actions in the Holy Land, Sicily and Constantinople itself. Beyond that, matters grow somewhat hazy.

Much of what we know about Harald derives from Icelandic sagas, poems and histories, supplemented by Byzantine sources, such as Michael Psellus’s “Chronographia.” In “The Last Viking,” Hollway, a journalist specializing in military history, dramatically weaves together all the facts and most of what is conjectured about the Viking, the result being at once a biography and “a melding, comparison and recounting of the old tales.” Was the handsome blond warrior a favorite of the aging, lustful Empress Zoe? Did he gouge out the eyes of the pusillanimous Emperor Michael V? Was he the secret lover of the Emperor Constantine IX’s mistress? Might the imperial throne have actually been within reach of his sword-arm? Though it’s impossible to be sure, all of these questions could plausibly be answered “yes.” That’s what the ­skalds and chroniclers believed and that’s the riveting story Hollway tells.

In the year 1030 Harald was 15 years old when he joined his much older half brother Olaf, the deposed king of Norway, in the latter’s attempt to regain his throne. Just before the climactic battle of Stiklestad, Olaf told Harald he was too young for the upcoming clash of arms, to which the teenager reportedly countered, “I will certainly be in this battle. I’m not too weak to handle a sword. If necessary my hand can be strapped to the hilt.” During the fighting, Olaf was killed and Harald left for dead. But the boy survived, recovered from his wounds, and with a small company headed for Russia, traveled up the Neva River to Lake Ladoga and then on to Kiev, where his kinsman Prince Yaroslav ruled. Three years later, only 18, Harald captained that prince’s household guard. Recognizing that he could rise no higher in Kiev, this ambitious, natural-born commander sailed and portaged down the river Dnieper, then crossed the Black Sea to Miklagard, the Big City, as the Scandinavians called Constantinople.

Hollway devotes half his book to Harald’s adventures and machinations during the decade he spent with the Varangian Guard. Toward the end of those years, the Viking and his closest lieutenants were cast into a lightless dungeon, yet nonetheless managed to break out, kidnap the emperor’s mistress and commandeer two galleys. But so what? Escape by sea was blocked by a heavy barrier chain stretched across the estuary known as the Golden Horn. Ever resourceful, Harald ordered his men to row toward it with all their might just as he and the others on board all rushed to the ship’s stern. This raised its bow high enough so that the vessel rode halfway over the chain, at which point everyone immediately raced forward to elevate the galley’s back half, allowing the ship to slide down into open water.

Once back in Kiev, Harald married Yaroslav’s pretty daughter Elisaveta, then journeyed homeward to seize power in Norway and attempt to subjugate Sweden and Denmark. Up to this point, the Viking could be construed a hero or at least a brilliantly audacious and quick-witted soldier of fortune, but in his unrelenting drive to be ruler of all Scandinavia he soon grew treacherous and cruel, looting and burning Danish cities, murdering any nobles who stood against him. His battle standard, white silk bearing the image of a black raven, became known as Land-Waster. The chance to bring England under its sway ultimately led to Harald’s last stand at Stamford Bridge.

A fencer and historical reenactor, Don Hollway excels at describing medieval weaponry, shield walls and battle tactics. Yet this isn’t just a book for military history buffs. If you love Frans Bengtsson’s picaresque masterpiece, “The Long Ships,” Robert Graves’s intrigue-suffused “I, Claudius,” or heroic fantasy in the mold of Robert E. Howard, George R.R. Martin and Howard Andrew Jones, you owe it to yourself to pick up “The Last Viking.” It’s that exciting, that good.

Michael Dirda reviews books for Style every Thursday.

The Last Viking

The True Story of King Harald Hardrada

By Don Hollway

Osprey. 368 pp. $30