Question: Where were the Danish Vikings most active?
About the article "Denmark", section "Viking and Middle Ages".

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Most records name the jarl of Jomsborg Sigvald(i), son of petty king Strut-Harald of then Danish Scania.
Sigvald died some time before 1010.
The Jomsborg Vikings (Jomsvikings) were composed of selected warriors, adhered to a special codex, and were loyal only to their leader.
In 1009, many Jomsvikings left Jomsborg and followed Sigvald's brothers Herring and Thorkell the Tall to England, where they became the nucleus of Cnut the Great's Thingmen or Huscarls. 
In an era where color TVs were rare, the Vikings (along with several other NFL teams) wore white jerseys for home games for the 1964 NFL season.
This allowed fans to see the visiting teams' primary colors.
In the 1960s the Vikings wore purple pants with road white jerseys.
On October 11, 1964 the Vikings played the Detroit Lions at Metropolitan Stadium and the Lions mistakenly only brought their white jerseys to Minnesota.
Both teams started the game in white, but by the second quarter the Vikings were able to obtain their purple tops.
The Vikings changed jerseys on the sidelines during the 2nd quarter, finishing the game in purple jerseys and purple pants.
It wasn't until 43 years later, on December 17, 2007 (a Monday Night Football game versus the Chicago Bears) that the Vikings again donned both purple jerseys and purple pants (However, the 2007 game marked the first time the Vikings wore all-purple intentionally).
Three years later, the Vikings played the November 7, 2010 home game against the Arizona Cardinals in the all-purple uniform.
In the ensuing years, the Vikings have donned the all-purple look from time to time, typically at least once a season.
They most recently wore all-purple on October 27, 2013 vs. Green Bay. 
The museum covers 14,000 years of Danish history, from the reindeer-hunters of the Ice Age, Vikings and works of art created in praise of God in the Middle Ages, when the church played a huge role in Danish life.
Danish coins from Viking times to the present and coins from ancient Rome and Greece, as well as examples of the coinage and currencies of other cultures are exhibited also.
Furthermore the National Museum keeps Denmark’s largest and most varied collection of objects from the ancient cultures of Greece and Italy, the Near East and Egypt.
For example, it holds a collection of objects that were retrieved during the Danish excavation of Tell Shemshara in Iraq in 1957.
In addition to this, there are exhibits about who the Danish people are and were, stories of everyday life and special occasions, stories of the Danish state and nation, but most of all stories of different people’s lives in Denmark from 1560 to 2000.
The Danish pre-history section was re-opened in May 2008 after years of renovating.
In 2013, a major exhibition on the Vikings was opened by Queen Margrethe: it is due to tour to other museums, including the British Museum in London. 
"Vikings" was a common term for Norsemen in the early medieval period, especially in connection with raids and monastic plundering by Norsemen in the British Isles.
The Norse were also known as "Ascomanni", "ashmen", by the Germans, "Lochlanach" (Norse) by the Gaels and "Dene" (Danes) by the Anglo-Saxons.
The Gaelic terms "Finn-Gall" (Norse Viking or Norwegian) and "Dubh-Gall" (Danish Viking or Danish) and "Gall Goidel" (foreign Gaelic) were used for the people of Norse descent in Ireland and Scotland, who assimilated into the Gaelic culture.
In the eighth century the inrush of the Vikings in force began to be felt all over Pictland.
These Vikings were pagans and savages of the most unrestrained and pitiless type.
They were composed of Finn-Gall or Norwegians, and of Dubh-Gall or Danes.
The latter were a mixed breed, with a Hunnish strain in them.
However, British assumptions of where the vikings came from were not quite correct.
Those who plundered Britain lived in what is today Denmark, Scania, the western coast of Sweden and Norway (up to almost the 70:th latitude) and along the Swedish Baltic coast up to around the 60:th latitude and Lake Mälaren.
They also settled on the island of Gotland.
The border between the Norsemen and more southerly Germanic tribes, the Danevirke, today is located about south of the Danish-German border.
The southernmost living vikings lived no further north than Newcastle-upon-Tyne, and travelled to Britain more from the east than from the north.
The northern part of the Scandinavian peninsula (with the exception of the Norwegian coast) was almost unpopulated, but the few who lived there were Sami, the native people of northern Sweden and large areas of Norway, Finland and the Kola peninsula in today's Russia.
The Slavs, the Arabs and the Byzantines knew them as the "Rus"' or "Rhōs", probably derived from various uses of "rōþs-", i.e.
"related to rowing", or from the area of Roslagen in east-central Sweden, where most of the vikings who visited the Slavic lands came from.
Archaeologists and historians of today believe that these Scandinavian settlements in the Slavic lands formed the names of the countries Russia and Belarus.
The Slavs and the Byzantines also called them "Varangians" (ON: "Væringjar", meaning "sworn men" or from Slavic "варяги" supposedly deriving from the root "вар"—"profit", as coming from the North they would profit by trading goods and not producing them, which had a negative connotation in Slavic culture of that time), and the Scandinavian bodyguards of the Byzantine emperors were known as the Varangian Guard. 
The most important primary sources on the Vikings are various sorts of contemporary texts from Scandinavia and regions where the Vikings were active.
Writing in Latin letters was introduced to Scandinavia with Christianity, so there are few native documentary sources from Scandinavia before the late 11th and early 12th centuries.
The Scandinavians did write inscriptions in runes, but these are usually very short and formulaic.
Most contemporary documentary sources consist of texts written in Christian and Islamic communities outside of Scandinavia, often by authors who had been negatively affected by Viking activity.
These texts reflect varying degrees of bias and reliability, but not more so than is usually the case in early medieval writings, and they remain very important.
Later writings on the Vikings and the Viking Age can also be important for understanding them and their culture, although it needs to be treated very cautiously.
After the consolidation of the church and the assimilation of Scandinavia and its colonies into the mainstream of medieval Christian culture in the 11th and 12th centuries, native written sources begin to appear, in Latin and Old Norse.
In the Viking colony of Iceland, an extraordinary vernacular literature blossomed in the 12th through 14th centuries, and many traditions connected with the Viking Age were written down for the first time in the Icelandic sagas.
A literal interpretation of these medieval prose narratives about the Vikings and the Scandinavian past is of course doubtful to some extent, but many specific elements remain worthy of consideration, such as the great quantity of skaldic poetry attributed to court poets of the 10th and 11th centuries, the exposed family trees, the self images, the ethical values, etc.
all included in these literary writings.
Indirectly the Vikings have also left a window open to their language, culture and activities, through many Old Norse place names and words, found in their former sphere of influence.
Some of these place names and words are still in direct use today, almost unchanged, and sheds light on where they settled and what specific places meant to them, as seen in place names like Egilsay meaning 'Eigils Ø' ("Eigil's Island"), Ormskirk meaning 'Ormr kirkja' ("Orms Church" or "Church of the worm"), Ravenscar ("Ravens Rock"), Snaefell ("Snow Fell"), Vinland ("Land of Wine" or "Land of Winberry"), Kaupanger ("Market Harbour") and Tórshavn ("Thor's Harbour") for example or the religious center of Odense, meaning a place where Odin was worshipped.
It is also evident in concepts like the present day Tynwald on the Isle of Man.
Common words in everyday English language, like some of the weekdays (Thursday means "Thors day" fx.
), axle, crook, raft, knife, plough, leather, bylaw, thorp, skerry, ombudsman, husband, heathen, Hell, Norman and ransack stem from the Old Norse of the Vikings, and give us an opportunity to understand their interactions with the people and cultures on the British Isles.
In the Northern Isles of Shetland and Orkney, Old Norse completely replaced the local languages and over time evolved into the now extinct Norn language.
Some modern words and names only emerge and contribute to our understanding after a more intense research of linguistic sources from medieval or later records, such as York ("Horse Bay"), Swansea ("Sveinn's Isle") or some of the place names in Northern France like Tocqueville ("Toki's farm").
Linguistic and etymological studies continue to provide a vital source of information on the Viking culture, their social structure and history and how they interacted with the people and cultures they met, traded, attacked or lived with in overseas settlements.
It has been speculated that several place names on the west coast of southern France might also stem from Viking activities.
Place names like Taillebourg ("Trelleborg", meaning "city of thralls" or "castle of thralls") as far south as the Charente River for example.
Gascony and vicinity is an active area of Viking archaeology at present.
A lot of Old Norse connections are evident in the modern-day languages of Swedish, Norwegian, Danish, Faroese and Icelandic of course.
Old Norse did not seem to exert any greater influence on the Slavic languages in the Viking settlements of Eastern Europe.
It has been speculated that the reason was the great differences between the two languages, combined with the Rus' Vikings more peaceful businesses in these areas and the fact that they were excessively outnumbered.
The Norse did name a few of the rapids on the great Dnieper River, but this can hardly be seen from the modern names.
A consequence of the available written sources, which may have coloured how we perceive the Viking Age as a historical period, is that we know a lot more on the Vikings' activities in western Europe than in the East.
One reason for this is that the peoples living in northeastern Europe at the time were non-literate, i.e.
they did not produce a legacy of literature.
Another reason is that the vast majority of Scandinavian written sources come from Iceland, a nation originally settled by Norwegian colonists.
As a result there is much more material from the Viking Age concerning Norway than for instance Sweden, which apart from many Runic inscriptions, has almost no written sources from the early Middle Ages.