The Viking origins of your Bluetooth devices

Every day, thanks to Bluetooth technology, people across the world can connect wirelessly to listen to music, check out a podcast, or watch a movie. In the mid-1990s, its developer—Intel engineer Jim Kardach—was trying to think up a name for the new technology. Reading about Viking history at the time, he was intrigued by a stone inscribed with runes that praised the exploits of a 10th-century Danish king called Harald Bluetooth.

The stone described how Bluetooth had brought the Danes together as one people and conquered Norway. “It occurred to me that [his name] would make a good code name for the program,” Kardach wrote. Other names were considered, but the Viking ruler’s moniker stuck. Bluetooth technology set out to conquer and connect the modern world, just as King Bluetooth had connected and conquered swathes of Scandinavia more than a thousand years before.

(Facts vs. fiction: How the real Vikings compared to the brutal warriors of lore.)

Birth of a dynasty

Harald Bluetooth’s life spanned the 10th century. During his 30-year reign, he overran Norway, completed the conversion of Denmark to Gormsson Christianity, and erected fortresses to glorify his name. Although his life would end in strife with his son, Sweyn Forkbeard, his dynasty held firm: His grandson, Canute, would later rule England, Denmark, and Norway.

The Bluetooth moniker comes from Blåtand, which in Old Norse means “bluetooth” or “dark tooth.” Tradition says that the nickname came from the king’s having a darkened, or bad, tooth, but hard evidence of his dentition does not exist.

Bluetooth had another name: Harald Gormsson, or Gorm’s son. Exactly how his father Gorm rose to power is uncertain. He seems to have been a native Jutlander. In A.D. 936, Gorm took control of northern Jutland from the Swedes, creating a kingdom centered on the town of Jelling.

Gorm’s efforts to keep and pass on this realm to his heir reflects a general trend in 10th-century Scandinavia. Viking kingdoms had emerged in previous centuries thanks to wealth amassed through plunder around the North Sea. Later in the 900s, they started to develop into centralized monarchies. What Gorm began in Jelling, Bluetooth and his heirs consolidated. This Jelling dynasty was also shaped by another key transformation of the 10th century: the Christianization of Scandinavia.

(Explore the realm of the Vikings.)

The Bluetooth saga

Two famous rune stones at Jelling were impressive monuments to a new, stable style of rule. The older and smaller of the pair was inscribed by the pagan Gorm to commemorate Thyra, his wife and the mother of Bluetooth. The larger stone was raised by Bluetooth. On one side, it bears an engraving of Christ hanging from a tree, the earliest visual depiction of Jesus in Denmark. On another face is a runic inscription that would, centuries later, inspire the creator of Bluetooth technology: Sá Haraldr es sér vann Danmork alla auk Norveg auk dani gærði kristna (“Harald won for himself all of Denmark and Norway and made the Danes Christian).”

The claims inscribed on the Jelling Stones, are, of course, propagandist. For a more nuanced picture of Bluetooth’s achievements and failures, historians consult a variety of medieval sources. One key document is a saga written in Iceland in the 13th century by Óláfr Þórðar-son, the nephew of Snorri Sturluson, another famous chronicler of the Vikings. Entitled the Knýtlinga Saga, Óláfr’s account begins with Bluetooth’s accession: “He was a strong ruler, and a great leader in war.”

(These are some of the world’s most spectacular Viking artifacts.)

The saga then describes how Bluetooth set his sights on the kingdom of Norway, where his nephew Harald Gráfeldr (Graycloak) reigned. The chronicle suggests that Bluetooth conspired against Gráfeldr, who was invited to Denmark and assassinated there. After the Norwegian king’s death, Bluetooth invaded Norway with his army; appointed a vassal king, Håkon Jarl; and then forced the entire country to pay him tribute.

Converting the king

To the south, Denmark bordered a state far more powerful than the Viking kingdoms: the Holy Roman Empire. The emperors had been battling the Germanic and Slavic peoples for many decades under the pretext that these were pagans who needed to be converted to Christianity. This was also the justification used by Emperor Otto II when he counter-attacked Bluetooth in 974, a year after Bluetooth set upon his lands in Saxony.

(After pillaging France and Spain, Viking raiders set their sights on Rome.)

According to the Knýtlinga Saga, Otto “attacked the king of Denmark and tried to convert the Danes to Christianity, but the Danish king had no intention of embracing the Christian faith, and faced him [Otto] with his army.” With support from Norwegian reinforcements, Bluetooth not only staved off Otto’s offensive, but he also managed to seize territory south of the border. After the Norwegians withdrew, however, Otto regained lost ground and even moved north of the Danewirk, a defensive line of walls and trenches that had been the border between Christian and pagan lands.

The saga sows confusion as to when Bluetooth converted and whether there were religious motives for Otto’s offensive. It is likely that conversion happened in 965, some years before Otto’s attack. The most detailed extant account is found in Res gestae Saxonicae (Deeds of the Saxons), written in the late 10th century by Saxon chronicler Widukind of Corvey, a monk from northern Germany. Widukind states that even before Bluetooth’s conversion, the Danes had accepted Christ as a god while still worshiping their own deities, who they believed were more powerful. According to Widukind, Bluetooth received a priest called Poppo who had traveled from Cologne and spoke to the king about faith:

Poppo declared that there is one true God, the father, together with his only-begotten Son, Our Lord Jesus Christ, and the Holy Spirit; and the [Danish gods] were verily demons, not gods. King Harald, quick to listen and slow to speak, asks if Poppo wishes bodily to demonstrate this faith. Unhesitatingly Poppo affirms his willingness. The ... king orders a piece of iron to be heated, and demands that it shall be carried by Poppo. Now the confessor of Christ unhesitatingly carries the iron as far as the King orders. The priest then shows everyone his unharmed hand ... At this, the King decrees that Christ is to be worshiped as the only God. He orders all of his subjects to renounce the idols and honor the priests and servants of God.

(Christianity struggled to grow—until this skeptic became a believer.)

Resistance to religion

The transition to Christianity was not a smooth one, however. The Knýtlinga Saga recounts that Bluetooth forced the Norwegian vassal king, Håkon Jarl, and his men, who were at the Danish court, to be baptized. He then sent Håkon Jarl, along with priests, into Norway with a mission to baptize all Norwegians.

But Håkon Jarl remained unswayed by the new religion. After leaving the Danish court, he renounced the Christian faith and returned to Norway, where he set about offering lavish sacrifices to the Norse gods. Bluetooth was furious and led an attack that devastated the Norwegian coast. However, when Bluetooth’s forces returned to Denmark, Håkon Jarl regained control over Norway.

The road to Christianization was not smooth. Another episode in the Knýtlinga Saga show, despite his Christian zeal, Bluetooth himself hadn’t entirely abandoned his old beliefs. In mulling over whether to attack Iceland, he did not pray to his Christian god for guidance but rather “bade a sorcerer to journey to Iceland and find out what he could tell him.” When the sorcerer returned with news that the island was too far away and in any case inhabited by all manner of monstrous creatures, Bluetooth shelved his plans for invasion.

From 1872 to 1874, storms exposed 16 pieces of gold jewelry from the Viking era (circa 793-1066) on the beach of Hiddensee, a small German island in the Baltic Sea. The find consists of a neck ring, a disc-shaped brooch, and 14 pendants, of which 10 are in the shape of a cross. Although the style is fairly typical of 10th-century Viking metalwork, the use of pure gold is exceptional. What is most striking is the combination of Christian and non-Christian motifs in the decoration of the pieces. The top part of the cross-shaped pendant, for example, bears a bird’s head with protruding eyes. Such an elaborate set of golden jewelry must have belonged to a person of very high rank. The style suggests that they were made for a woman. The hoard has been dated to the reign of Harald Bluetooth, and many theories have been put forward as to how it ended up on Hiddensee, at some distance from the Viking lands where it was likely made. One theory proposes it was buried there by a Slavic pirate who operated along this coast.

Jutta Grudziecki/Stralsund Museum

Civil war in Denmark

Bluetooth was well known for his security measures to protect his lands. Following the threats posed by the incursions of the Holy Roman Emperor, Bluetooth had numerous circular fortifications built. These are now known as Viking Age Ring Fortresses, or Trelleborg-style forts. Building defensive structures on such a large scale required labor from warriors who normally formed the retinue of the jarls (noblemen, and the root of the English word “earl”).

Unhappy at losing their men, the jarls became discontented with Bluetooth, who, they believed, was abusing his power. This set the stage for the end of Harald Bluetooth’s reign. When Bluetooth’s son Sweyn was still young, he had claimed a share of the kingdom, but his father refused to give it to him. According to the Knýtlinga Saga, “since he [Sweyn] was the son of a concubine, his father had no great affection for him and refused to give him any land to rule over.” When Sweyn reached adulthood, he decided to act as the Vikings had always done and, after gathering a few ships and a strong band of supporters, likely recruited from his father’s opponents, he launched raiding expeditions in Denmark and abroad.

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Bluetooth raised an army and attacked his son’s forces. Several battles ensued, and the situation escalated into civil war. In one fight, Bluetooth’s troops finally defeated Sweyn’s, but in the fray Harald had been wounded. He died a short time later, in November 987, and is believed to have been buried at the church of Roskilde. If so, he was the first Danish king to be interred in consecrated ground.

Bluetooth’s long legacy

On his accession as Sweyn I, the feuds with the jarls subsided. In the period of relative peace that followed, Bluetooth’s fortresses were abandoned because they were costly to maintain. A fierce warrior king, Sweyn Forkbeard dedicated much of his reign to raids against England.

The world that Harald Bluetooth had helped forge continued to take shape during the dominion of Sweyn I, whose fellow monarchs in Norway and Sweden were all, by then, Christian kings. The Nordic world—including Iceland, which converted to Christianity around the year 1000—was being integrated into the spiritual map of Europe.

Estrid, Bluetooth’s granddaughter, gave her name to the Estridsen dynasty that ruled Denmark into the 15th century, and whose line of descent can be traced to Margrethe II, the current queen of Denmark. The exploits of Bluetooth’s descendant, Knútr inn ríki—better known as Canute—would have far-reaching consequences for English history.

('Denmark’s salvation'? Runestones hint at Viking queen's power.)

The raids on England carried out by Canute’s father, Sweyn I, had forced King Ethelred the Unready to flee in 1013. This allowed Sweyn a clear path to the throne as a short-lived King of the English. Following his father’s death in 1014, Canute was duly proclaimed King of the English, before being forced to retreat to Denmark by a returning Ethelred. Having assembled a fleet, Canute and his forces returned to England, defeating Ethelred’s son and successor, Edmund Ironside, in 1016.

As England’s new king, Canute stopped Viking raids, and ushered in a two-decade period of stability and prosperity. Two years later, he succeeded his brother as king of Denmark and expanded his territory. By 1028, the Jelling dynasty, consolidated by Harald Bluetooth, stretched from the southwest of England to the far northeast of Norway.