There is many reasons that the innhabitants of Scandinavia began traveling the seas and conduct trading operations, raids and colonizations.

The most important factor of them all is that they developed ships that made this possible. The viking ships where sturdy and shallow-draught ships. This enabled them to cross the North-Sea and at the same time basicly go wherever they wanted when they arrived. They could go up rivers or be dragged on a beach when you disembarked. It was the optimal ship for a world with bad harbor infrastructure.

There is also archeological evidence that in Scandinavia land was being cleared for farming. This is evidence of a growth in population in scandinavia and with an ever decreasing amount of unused land some of the population needed another way to survive than farming. With the Longships at hand expeditions both east- and westwards quickly became a good way of finding new land, money and wealth.

The countries in england and other places in Europe was also quite weak and divided. This allowed the vikings to roam free at the coast of Europe and attack where they wanted. This was not a reason for the raids to begin, but rather a reason for there to be so many of them. This was also one of the reasons the raids stopped. Over time the countries in Europe became stronger and more united, it therfore became more dangerous to try to attack them because they could now gather an army to face the viking threat.

Finally i read in a book that the viking raids was a respons to the aggresive missionary vork of the anglo-saxon, but i can find any other sources on this so unless anyone elsa can find anything about it i would not trust it too much.

I have mostly used a norwegian book called "Det ligger et land" and this page, wich is also in norwegian and is supervised and owned by the norwegian universities.

I hope my english was not too bad, and that the text was interesting. If you have any questions please ask and i will do my best.