Interracial marriage
From AD 839, Viking Varangian mercenaries who were in the service of the Byzantine Empire, notably Harald Sigurdsson, campaigned in North Africa, Jerusalem and other places in the Middle East during the Byzantine-Arab Wars. They interbred with the local population as spoils of warfare or through eventual settling with many Scandinavian Viking men taking Arab or Anatolian women as wives. There is archaeological evidence the Vikings had established contact with the city of Baghdad, at the time the center of the Islamic Empire, and connected with the populace there. Regularly plying the Volga with their trade goods (furs, tusks, seal fat, seal boats and notably female slaves; the one period in the history of the slave-trade when females were priced higher than males), the Vikings were active in the Arab slave trade at the time. These slaves, most often Europeans that were captured from the coasts of Europe or during war periods, and sold to Arabic traders in Al-Andalus and the Emirate of Sicily.
Swedes in the United Kingdom
The earliest wave of migration from modern day Sweden, Norway and Denmark came in the form of the Viking invasion of Britain in the year 793. Viking raids occurred up and down the largely undefended east coast of England and Scotland during the eighth and ninth centuries and Scandinavian settlements became established over the entire island of Great Britain, the most important of which was Jórvík (now York). Viking rule came to an end in the 11th century when Normans invaded the shores of Britain. Despite this, Scandinavian influence is evident in the UK even to this day and many millions of Britons have some Viking heritage (especially in Northern England, Eastern England, Scotland and the Shetland Islands).