From ScienceNordic:

Because the English natives failed to stop them?

February 23, 2017 – 06:25 Despite the dangers, between 20,000 and 35,000 Danish Vikings chose to uproot and migrate to England between the 9th and 10th century. So says a new study published in the archaeological journal Antiquity. Initially the trips were raiding expeditions, but later on, more and more Vikings decided to stay in the new land to the west, cultivate land, and “proceeded to plough and to support themselves,” according to the Anglo-Saxon Chronicle of 876. But why did so many Vikings say farewell to the security of their homeland, friends, and relatives to move to a new country? If you ask Viking researcher Søren Sindbæk, a professor with special responsibilities in the School of Culture and Society from Aarhus University, Denmark, the reasons behind the wave of migration in the 9th and 10th centuries were driven by the same factors that drive migration to Europe today: the chance of a better life. “It’s the same thing that made people travel to America or Australia a couple of hundred years ago. New transport options developed in the 9th century, and people began to use sailing ships on a large scale. At the same time, the Vikings who went to England to plunder, realised that they could also use their military power to acquire land,” says Sindbæk.

So why are modern Europeans ceding space to people without any military power?

The Viking’s initial trips to England were more or less unsystematic raids. But by the latter half of the 9th century, the Scandinavian Vikings had organised themselves into a large army, often referred to as the Great Heathen Army or micel here in Old English. … “The warriors of the Great Heathen Army managed to achieve a position of power, so they could expropriate large tracts of land and say, “Now we should own land here.” … “Today, we live in a time with large scale migration. We see many migrants and refugees coming to Britain, just like the rest of Europe. Migration is a part of our culture. We should open our eyes to the fact that the same happened 1,000 years ago, instead of thinking about our ancestors as people who were settled and never left their farm,” says Kershaw.

One Englishman who remembered it was part of their culture was Rudyard Kipling: