So this is a very loaded topic with a long history behind it. Nor is the same answer for the question possible in every country, fr example the relationship between the Old Germanic people and white supremacy is different in the United Kingdom compared to Germany, which is different from Scandinavia, which is in turn different from what happens in the United States. Today the connections between white supremacist groups and Neo-Nazis and Old Norse cultural imagery are well known, but this is something of an aberration in historical trends. So any answer to this question needs to deal with more than just the situation in Scandinavia circa the 9th century and more than just dealing with modern white supremacist groups.

Sadly though, as I mentioned above, this is not a unique trend to the Vikings/Old Norse people. The Middle Ages in general, and the Germanic peoples who settled in much of what is now Western Europe in particular, come in for this type of connection and association across the board and there are broadly two reasons for it, everyone's two favorite -ism's from the 19th century. These are nationalism and racism, and the horrid offspring of these two, scientific racism, filtered with a little dash of unique political circumstance and popular culture.

To talk about this connection between white supremacy and the Norse peoples we need to go back to the beginning. Not to the Middle Ages mind you, but to the imagined Middle Ages of the 19th Century. The time of wandering tribes, wholesale slaughter of native communities, racial purity, and the creation of the modern peoples that were slowly on the march to unification in the modern era. Now this was of course not a real time that actually existed, it was a creation largely of romantic thinkers, artists, and the first historians of the time who were a long ways off from modern understandings. In the romantic/19th century mind, the Middle Ages were a simpler, purer, more authentic time than the modern day, and I will touch on this later.

The 19th Century was a weird time in world history. For much of the previous several centuries, the nations of Europe strove to connect their history and peoples to the world of Classical Antiquity. This was not new to the pre-modern world though, even in Late Antiquity authors were trying to connect their own ethnic groups to the Homeric world or to Alexander the Great, think of the Icelandic author Snorri Sturluson who posited that the Norse gods came from Troy and Africa, or the Britons who came from Troy too, there was a lot of connecting various ethnic groups to ancient Troy (it worked for the Romans after all!)

However, by the 19th century this was starting to fall out of favor in many western countries and instead new connections were being drawn not only to ancient Rome but also to the "barbarian" peoples who either preceded the Romans, think the Gauls of France, or who supplanted them, the "Anglo-Saxons" of Britain, the Germanic peoples of....Germany, the Franks, the Lombards, and of course the Vikings. The thinkers of this time connected the essence of the nation and the people with the rural peasantry and their supposed deeply rooted connection to the land of their ancestors. This form of nationalism/centrism is often termed "Blood and Soil" and gained immense popularity and cachet during the Third Reich for example, but it was seen, if called something sightly different, in many European countries that were seeking new national myths to unite their countries. This whole process was in many ways a reaction against the industrialization, urbanization, and capitalization of the 19th century economy, and social, economic, and cultural upheaval wrought by industrialization birthed many new economic, political, and cultural movements such as romanticism, that on one hand gave us the poetry of figures like Byron and Shelley, but on the other hand also gave their societies and intense desire to explain and rationalize their experiences as a national whole, and the connections that were made tended to be drawn to the early Middle Ages, the time of the migrations, and the wholesale movement of entire ethnic groups in grand conflicts that shook the world to its core.

Now of course in the 21st century we know that many of the nationalistic stories that were told and emphasized in the project of building national cohesion were just that, stories, but at the time the intellectual elite of countries like Germany, the UK, and France places immense stock in their national origin myths, such as the defiance of the Romans by figures like Arminius, the baptism of Clovis, the conquest of England by the Angles and Saxons. The nationalist ambitions of these western countries were fueled in large part by medievalism, or the use of medieval history and imagery in the modern day.

This is where I will narrow the focus, as while France, Britain, Italy, and other countries had these same nationalist impulses derived from Romanticism and other movements of the 19th century, in Germany, and the "Germanic" lands of Europe this particular strain of nationalism took on immense political importance (as it did in other countries, but that is a train of thought for another day). In Germany, at the time Germany was divided in numerous states, the incipient movements of nationalism, romanticism, and scientific movements such as Darwinism combined in the literary/cultural/scientific intelligentsia of the western world, informed often by developments in other countries, especially the racial politics and "science" of the United States, a variety of ideas were floated that sought to explain European power in the world today, and connect it back to the mythologized past that inhabited the minds of these 19th century thinkers.

Enter racial "science". Many Europeans, and Americans sought to explain the power of European countries, and the US, by connecting it back to innate biology. Influenced heavily by ideas such as Darwin's theory of evolution via natural selection, many figures of the 19th century arrived at the conclusion that European societies were more fit than other societies around the world, and others went even further still. Influential "thinkers", to use the term generously, in Europe and America believed that even among Europeans there were racial subdivisions that could explain even more. Among these divisions were the origins of "Celtic" peoples, "Mediterranean", "Slavic", and more, but the most influential of these, and the most directly relevant to your question here is the idea of a Northern European race that was physically, intellectually, and culturally not only distinct to the rest of Europe but superior to it. This was proven by their success in colonization, military adventurism, advanced economies, and scientific progress.

The naming conventions vary by author, time, and country so I will refer to this as "Nordic" though at times this hypothetical, (and it must be emphasized non-existent) group of Northern European people with distinct racial characteristics, has been referred to as Teutonic, Germanic, Aryan, and so on. This gave rise to Völkisch thought which emphasized the German people's racial purity, unity, and strength. For my purposes here, the emphasis on Nordic racial groups is not entirely synonymous with Völkisch ideology. Nordic racial thinkers were far more geographically widespread, being found in positions of power and influence in the United States, the UK, France, Australia, Canada, New Zealand, Germany, Austria, and others, whereas Völkisch political movements and ideology are significantly more influential in German speaking Europe and Scandinavia. The two are not identical phenomena but they are deeply related.

The impact of this idea of Nordic superiority cannot be overstated. Scientists, economists, politicians, philosophers, and more attributed he success of the British Empire, the rise of the United States, and the German Empire to the biological superiority of the "Nordic" peoples, who they believed were the reason behind the success of their modern descendants. Indeed they attributed the success of almost every state in history the primacy of the Nordic race. The Romans? Ruled by a Nordic elite, and the same for the Greeks for example. It was only over time through the weakening of the racial purity of the Nordic elite, according to these 19/20th century thinkers, that these states were able to collapse, only to be surpassed in the Middle Ages by the more racially pure descendants of the Nordics who had stayed in Germany and Scandinavia. The descendants of those states therefore had to maintain their purity to stay strong and vibrant and win out over the lesser races of the world.

Now the homeland of these people was assumed to be Scandinavia and here is a pretty good map from one of the seminal works of this field. Therefore the people of Scandinavia such as the Norse were connected deeply to this field of racial science and ideology. This was further enhanced in the arts of this time period, and German opera pieces such as Wagner's Der Ring des Niebelung further tied German states such as Austria, Germany, and the Nordic countries, to the imagined pan-Germanic past that produced the later countries.

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