Muslims conquests in Europe disrupted traditional trade, encouraging the Swedes to open up alternative routes through Russia.
Apparently the Slavs then begged them to take charge of their territory. “Our land is large and fruitful but it lacks order,” the message allegedly read. “Come over and rule us.”
By 900, Swedish influence radiated throughout Eastern Europe from their strongholds Novgorod and Kiev. The Swedes were soon assimilated under the weight of Slavic numbers, but they left an indelible mark in the name by which they were locally known, Rus.
Polygamy and primogeniture also shaped the Viking Age. Only a tiny proportion of Scandinavia was actually habitable, and farmland could only be subdivided so many times. The whole of patrimony generally went to the eldest son, or rather the eldest surviving son, so Swedish kings with 40 women in their harem, or Norwegian earls with a dozen sons by various wives and concubines, were sure recipes for orgiastic fratricide.
Harald Fairhair’s ascendancy, c. 890, went a long way towards defining Norway, but as he stropped and disbanded numerous lesser dynasties, their scions were compelled to try their luck abroad.
To begin with, Viking enterprise abroad was a matter of independent initiative, as epitomized by a certain Hasting. Born in Denmark, his first foray in 844 opened with a rebuff at La Coruña on Spain’s Atlantic coast, improved with the sacking of Lisbon, Cádiz and Seville, and ended with the loss of two ships crammed with gold, silver and prisoners to the Moors.