The Age of the Vikings lasted from about 800 to 1100 A.D. During this time their influence extended from their origins in Scandinavia throughout most of Europe, Byzantium in Asia Minor, and westward to North America.
There is proof of a Viking settlement on the island of Labrador off the Canadian coast, and the existence of Vinland, a Norse settlement farther south, is believed to have been in present day Nova Scotia, Rhode Island or Cape Cod. The discovery of a runestone in Minnesota with Nordic characters engraved on it, along with other purported Viking relics, seems to point to a Viking foray into interior North America.
The Viking impact on Europe was much more profound.
Though popularly depicted as looting and pillaging brutes, these Norsemen were also traders and settlers. They established trade routes to Constantinople and the Middle East through the rivers of Russia to the Black Sea. They settled along those waterways and are often credited with the very founding of the state of Russia. In Western Europe they were busy raiding the rich cities and settling in the British Isles and France.
The Slavic lands of East Central Europe, including Poland, were not as interesting to the Vikings. The wealth lay to the west and more convenient trade routes to the east. In addition, the Polish Slavs proved to be able defenders of their lands. Nevertheless, the region did see a Viking presence. Prior to the founding of the Polish nation in 966, they would have encountered individual Slavic tribes, and afterward only a loose confederation that was Poland. And the Slavs extended well to the west along the Baltic in Pomerania and what is now northeast Germany, abutting Denmark. This area was called Wendlands after the Polish Wends who lived there. They were not easy neighbors for the Danes, and while Vikings pillaged Western Europe, the Wends in turn attacked Viking strongholds in Denmark and southern Sweden. These marauding Wends were also sometimes called Slavic Vikings.
Legend holds that Wolin Island in the Odra delta just north of Szczecin was settled in the late tenth century by Jomsborg Vikings who fled Denmark. Supposedly, they came with the permission of Polish King Bolesław Chrobry and in return defended Poland. The Wolin population became increasingly Slavic and this mixed band of warriors raided Danish and Swedish towns, and for a time held the Baltic island of Ruegen. Historians say Wolin was not so much a true Viking outpost but a pirate base, and that the Jomsborg Vikings never existed. The Wolin stronghold was destroyed by King Magnus of Denmark and Norway in 1043.
No sagas of Viking settlements or raids into interior Poland exist. However, evidence of their presence has been found. In Elbląg, not Polish at the time but Slavic Prussian, Norse weapons have been uncovered, as well as a small cemetery with Viking elements. In Lutomiersk near Łódź, a tenth century cemetery was unearthed that yielded objects connected to Sweden. Some observers see similarities to Norse runic signs on some Polish coats of arms.
There is only scant archeological evidence of Viking trade routes up the Odra and Vistula Rivers through the heart of Poland to eastern Germany and the Black Sea, but they most likely did exist. One must assume some sort of contact with the Poles living along those waterways.
Polish-Wendish settlements supposedly existed near present day Hamburg, Germany and possibly in Denmark and Sweden. The Swedish town of Wendel may have been founded by Poles. Some researchers suggest that Slavic or mixed Slavic-Scandinavian Vikings were among the settlers in Iceland and Greenland. There is even a claim that two Polish knights named Wyzdarwoda and Tyrker accompanied Leif Ericsson to North America. Norse sagas identify Tyrker as the one who first discovered grapevines there, after which the Vikings called that country Vinland.
Poland is also tied to the Scandinavians and Vikings through royal marriages. Świętosława, daughter of Prince Mieszko, founder of the Polish nation, married Danish King Sven Forkbeard. In Denmark she was known as Gunhilda and her son was Canute, also a King of Denmark. Canute also conquered England and was aided in this endeavor by his uncle, King Bolesław of Poland, who sent Polish troops to help his nephew. And one of Bolesław's daughters was married to King Olaf Tryggvason of Norway. A claim that Prince Mieszko could be of Viking descent is highly speculative, seemingly based on the fact that Scandinavians referred to him as Dagome, a Scandinavian name, in early documents.
Finally, genetic research has shown that about seven per cent of persons of Polish descent belong to a DNA subgroup that shares a distant common ancestry with many people in England and Scotland. These persons' common ancestor may have been a Pomeranian Slav sent to invade England with Canute.
After a few centuries of German rule, Wolin Island is again part of Poland. Each year on the island a group of enthusiasts holds a Viking festival to celebrate the area's connections to that era. Re-enactors also stage a Viking festival in Rynia, twenty miles outside of Warsaw, where a replica of a Viking settlement has been built.
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I recommend this book about Polish history written by Adam Zamoyski and entitled: The Polish Way: A Thousand-Year History of the Poles and Their Culture