The medieval naval battles of Svold (c.1000) and Nisa (1062) between two rival Viking fleets demonstrates the flexibility of Scandinavian tactics, essentially bringing land tactics to naval battles as a form of medieval marine warfare. These tactics married the Norse warriors’ proficiency in hand-to-hand combat with their love of maritime technology, most notably their trademark warship, the longship.  This vessel was their primary instrument of overseas aggression during the Viking Age (793-1066). Long, narrow-keeled, and relatively flat-bottomed vessels with beautifully carved arched prows, the first longships carried around thirty-five sailors who also did double duty as warriors (whereas in contemporary Mediterranean galleys, the crew consisted of rowers and a separate deck crew with officers, and sometimes with a separate contingent of marines). They were made of oak using clinker construction (overlapping planks held together with clinch bolts) with a mast amidships and one bank of oars on each side. Controlled with a starboard-side steering oar, these vessels had shallow drafts making it possible for them to navigate up rivers and along coastlines, giving the Vikings unprecedented strategic mobility. The Gokstad ship, built in the second half of the ninth century, was over seventy-six feet long, twelve feet wide and drew less than thirty-four inches of water, giving it the ability to sail up rivers and estuaries into shallow waters only three feet deep. Longships were also easy to beach or portage over short distances using rollers and manpower, allowing them to sail up to the headwaters in regions like the Eastern Baltic and then portage to the headwaters of an entirely different river system in Eastern Europe, before sailing downriver.       

After 1000 CE, the Scandinavians built larger warships, some known as drakkars (“dragon ships”) because of intricate dragonheads carved into their prows. These larger, taller vessels were particularly suited for the last purpose because unlike longships, drakkars had high, planked decks fore and aft, from which arrows and spears could be rained down on their opponents’ decks. Furthermore, drakkars were capable of carrying as many as eighty warriors on raiding expeditions, invasions, and curiously, large naval engagements against rival Viking fleets. Difficult to maneuver in battle, these medieval dreadnoughts were sometimes lashed together “stem to stem and stern to stern” to create large, floating battlefields of oak, canvas, and rope. Often dozens of Viking ships were tied together, with the larger ships placed in the middle of the line as a command post for kings and commanders, while unfettered longships protected the flanks of the tethered vessels. The medieval Danish chronicler, Saxo Grammaticus (c.1150-c.1220), explains the benefits of lashing ships together for combat:

"Having ordered the ships in a line, they joined them together with grapples, so that being bound together the fleet might easily ride down any enemy in its path.  And when they were brought together for this purpose, they were joined together solidly, for flight or victory, as it would not be possible for anyone to break free from his colleagues.  Thus, they planned to make their weakness strong by this tactic." 

Photo top right: The Gokstad Ship. Viking Ship Museum, Oslo, Norway. The Gokstad Ship in the purpose-built Viking Ship Museum in Oslo, Norway. The ship is 24 meters long and 5 metres wide, and has room for 32 men with oars to row. Source: Wikipedia, in the Public Domain. 

Photo second from top: Illustration of Viking ship-to-ship warfare by modern illustrator Angus McBride. Source: Reddit; in the Public Domain, no rights listed or advised.

Not built for ramming, Viking ships could not duplicate the tactics of the ancient Greek triremes, therefore medieval sea battles usually consisted of closing on an opposing vessel, grappling the two ships together and then fighting in close quarters until one side was defeated, the enemy ship captured, or if damaged, scuttled. In the case of large engagements, one side chose to take the defensive by lashing their ships together, while the attacking navy either moved in on the tethered flotilla as individual ships, grappling, clearing, and cutting away ships one-by-one, or attacked as a tethered armada itself. In these ship-to-ship battles, the Vikings attempted to match larger ships to smaller and favored missile fire from bows and spears over hand-to-hand shock combat.  Because of the nature of this form of attrition warfare, Viking sea battles tended to drag on far longer than engagements fought on land, often taking hours to conclude.

A decisive Viking ship-to-ship battle took place in September around the year 1000 at the battle of Svold (sometimes Svolder) between King Olaf I Tryggvason of Norway (r.955-1000) and an alliance of Svein Forkbeard of Denmark (r.986-1014) and King Olof Skötkonung of Sweden (r.955-1022) and Olaf’s enemies in Norway, the jarl of Lade Erik Hakonarson (c.960s-1020s).  Although the exact location of the battle is disputed, it most likely took place in the Baltic Sea near the island of Rügen off the Pomeranian coast of what is today Poland. Olaf’s conversion to Catholic Christianity and his desire to centralize control of Norway under his rule led to friction with his pagan subjects and nearby pagan Scandinavian kings and jarls. This friction would lead to an all-out war as Olaf led a fleet into the Baltic, including his own drakkar, the Long Serpent, other longships of various sizes, and smaller boats used as coastal raiders. Contemporary sources often quote the size of this flotilla at eleven ships, but it was most likely much larger based on the tactics used by both combatants during the battle. In the southern Baltic, Olaf attempted to form an alliance with the Jomsvikings who settled in a Danish enclave on the southern Baltic coast. Led by Sigvaldi Strut-Haraldsson, the Jomsvikings were a pagan mercenary band who adhered to a strict military code among their own members, but who would serve both pagan and Christian if the price were right. And it was under this pretense the two leaders met.  However, according to Icelandic chronicler Snorri Sturluson (1179–1241) in his Heimskringla, Sigvaldi negotiated with Olaf while in port in a ruse to delay the Norwegian fleet as his secret Scandinavian pagan allies prepared an ambush. 

King Olaf’s fleet left harbor in open order, the smaller ships going ahead.  Meanwhile, King Svein and King Olof’s fleet lay hidden by an island described by the sources as Svold, although its precise location is still unknown. The smaller vessels were allowed to pass, but as Olaf and his large ships came closer, Svein’s numerically superior force attacked the now divided fleet. Contemporary sources differ on the size of the attacking flotilla, ranging from eighty to 140 vessels, but all agree that Olaf was outnumbered. In response, Olaf quickly lashed his smaller fleet together in line abreast as the Danish and Swedish fleets formed for a frontal attack while Jarl Erik led disenfranchised Norwegians and other Vikings against the enemy flank.  However, the frontal assault faltered as Olaf’s ships were so closely tied together that only their prows could be attacked. Additionally, many of the tethered ships were larger vessels with high sides and platforms from which defenders threw spears and other projectiles and fired arrows down on their attackers. Frustrated, some of the Danish and Swedish ships turned away to join Jarl Erik’s assault on the enemy flanks. Here, the attacking Scandinavians had more success, boarding the enemy amidship, clearing ships of their defenders before cutting them adrift and moving to the next vessel.  Eventually, Erik’s men cleared and removed the flanking ships one-by-one until they came alongside and boarded King Olaf’s Long Serpent. The defenders repulsed this first assault, but with the aid of reinforcements, a second succeeded with pagan Vikings boarding the flagship and cutting their way towards the Christian Norwegian king.  Various sources have different endings for Olaf, with some stating that he jumped overboard in full armor to commit suicide, while others maintain that he swam ashore and converted to Christianity, only to die in a monastery.  No matter what his fate, Scandinavia faced decades of slow and sometimes violent conversion from paganism to Christianity, accompanied by numerous power struggles as princes tried to expand and consolidate control over the Western Baltic.

Photo second from bottom:  “The Battle of Svolder” (1884). Painting by Otto Sinding (1842-1909). The Battle of Svolder, at which the Jomsvikings fought with Denmark against Norway, maybe with a swap of allegiance to side with Forkbeard's advantage, of his 400 ships to Tryggvason's 100. Source: Wikipedia; Public Domain. 

Photo at bottom: The Íslendingur, a seaworthy replica of the Gokstad Ship. Viking World Museum, Njarðvík, Iceland. Source: Wikipedia; in the Public Domain. 

Another famous Viking sea battle took place at Nisa on August 9, 1062, between the fleets of King Harald III Hardrada of Norway (r.1046-1066) and King Svein Estridson of Denmark (r.1047-1074). This was the second battle between the two rival monarchs and seems to have been joined by mutual consent.  Harald Hardrada, unhappy about being unable to conquer Denmark despite successful annual raids, hoped for a large decisive victory over Svein. Raising a large army from the whole of Norway, Harald placed them on three hundred ships, leading the armada from his own seventy-oar drakkar. Sailing to the appointed spot at the prearranged time, Hardrada waited for his Danish foe to arrive, but Svein’s fleet was not there.  Believing the Danes had refused battle, Hardrada dismissed half of his ships containing the militia to return to their farms and prepared for another year of raiding. Those warriors who remained were the veterans of numerous raids, and some may have fought at Hardrada’s side during his days in Russia and Byzantium. One of the Varangian Guard’s more distinguished soldiers, Harald spent most of his twenties in the Byzantine Emperor’s employment, rising to become the “leader of all of the Varangians” and then returning to Norway to become king in 1047.

But as half of the Norwegian navy sailed out of sight, the Danish fleet appeared three hundred ships strong. Refusing to flee from his numerically superior enemy, Harald ordered his remaining ships lashed together, placing his own drakkar in the center of the line.  Unfettered longships protected the flanks, including the warships of Jarl Hakon Ivarsson.  Mirroring the Norwegians, Svein ordered his warships roped together in a line, his own ship in the center, and seizing the initiative, rowed against the enemy.  As the tethered Danish line slowly rowed forward, Harald ordered his own Norwegian fleet to meet the advancing Danes. The two bound Viking armadas clashed as the sun began to set. 

According to both Danish and Norwegian sources, the battle lasted throughout the night with both sides evenly matched. The prominent role of archery in ship-to-ship combat is evident from a poem written about Hardrada’s prowess as an archer. Again, Snorri Sturluson tells us in his Heimskringla:       

“Norway’s king was bending his bow throughout the night,

Raining a shower of arrows on the white shields of Denmark.

Bloodied spear points open holes in iron armor.

Shields were pierced by arrows from Harald’s deadly dragon.”                                          

Harald Hardrada’s prowess with a bow was not unusual, and Viking sources tell us that numerous Viking heroes died by arrows, including Svein Forkbeard’s immediate predecessor, King Harald Bluetooth (r.958-986) and, ironically, perhaps Harald himself at the battle of Stamford Bridge just four years later.

The turning point came hours into the battle when Jarl Hakon ordered his warships from their flanking position to sail around the main battle group and prey on smaller and weaker Danish vessels Hours later, Hakon’s warships buttressed a failing flank, forcing the Danes back.  Svein’s warship was the last boarded. No quarter was given, and those Danes not killed jumped overboard. By dawn Svein’s fleet was defeated and no less than seventy of the Danish king’s tethered ships had been cleared and captured. The Danish king escaped the slaughter by jumping into the water and swimming for Hakon’s ship. Donning a disguise, the Svein was brought onboard and inexplicably led to shore on Hakon’s order, eventually escaping back to Denmark. Though initially recognized as the hero of the battle, the jarl was quickly condemned by the Norwegian king and exiled. Ultimately, the battle of Nisa proved indecisive. Two years later in 1064, the two kings signed a peace treaty ending years of Norwegian raiding, and Harald Hardrada looked to the west for new lands to conquer, finally dying on the battlefield in England against the forces of the Anglo-Saxon King Harald Godwinson (r.1066) at the battle of Stanford Bridge in 1066. 

Suggested Readings:

Primary sources

Friis-Jensen, Karsten, and Peter Fisher, eds. Gesta Danorum. Oxford Medieval Texts, 2015. 

Sturluson, Snorri. Heimskringla: History of the Kings of Norway. Translated by Lee M. Hollander. University of Texas Press, 2010.

Secondary sources

Devries, Kelly. The Norwegian Invasion of England in 1066. Boydell & Brewer, 2003.

Howard, Ian. Swein Forkbeard’s Invasions and the Danish Conquest of England, 991-1017. Boydell, 2003.

Marsden, John. Harald Hardrada: The Warrior’s Way. The History Press, 2011.

Sawyer, Peter. The Oxford Illustrated History of the Vikings. Oxford University Press, 2001.