The Vikings sailed most of the North Atlantic, reaching south to North Africa and east to Russia, Constantinople and the middle east, as looters, traders, colonists, and mercenaries. Vikings under Leif Eriksson, heir to Erik the Red, reached North America, and set up a short-lived settlement in present-day L'Anse aux Meadows, Newfoundland and Labrador, Canada.
The motives driving the Viking expansion form a topic of much debate in Nordic history. One common theory posits that the Norse population had outgrown agricultural potential of their Scandinavian homeland.For a coastal population with superior naval technologies, it made sense to expand overseas in the face of a youth bulge effect. However, this theory does little to explain why the expansion went overseas rather than into the vast, uncultivated forest areas on the interior of the Scandinavian Peninsula. It should be noted that sea raiding was easier than clearing large areas of forest for farm and pasture in a region with a limited growing season. No such rise in population or decline in agricultural production has been definitively proven.

Another explanation is that the Vikings exploited a moment of weakness in the surrounding regions. For instance, the Danish Vikings were aware of the internal divisions within Charlemagne's empire that began in the 830s and resulted in schism. England suffered from internal divisions, and was relatively easy prey given the proximity of many towns to the sea or navigable rivers. Lack of organized naval opposition throughout Western Europe allowed Viking ships to travel freely, raiding or trading as opportunity permitted.
The decline in the profitability of old trade routes could also have played a role. Trade between western Europe and the rest of Eurasia suffered a severe blow when the Roman Empire fell in the 5th century. The expansion of Islam in the 7th century had also affected trade with western Europe. Trade on the Mediterranean Sea was historically at its lowest level when the Vikings initiated their expansion. By opening new trade routes in Arabic and Frankish lands, the Vikings profited from international trade by expanding beyond their traditional boundaries. Finally, the destruction of the Frisian fleet by the Franks afforded the Vikings an opportunity to take over their trade markets.