Vikings were feared all across Europe. They were ruthless, and their newer fighting techniques were far better than the rest of Europe.
On this day March 28th, in 845, the Vikings sack Paris. In exchange for leaving and not killing people, the Vikings demanded a hefty ransom, which they eventually would receive. The Vikings were Norse explorers and conquerors. They are recognized by their horned helmets they wore into battle, as well as axes and maces. Vikings had a very profitable business of ransoming towns, and boarding ships, and generally are considered the pre-pirates which became prevalent a few centuries later.
What gave the Vikings the ability to get into Paris were the ships they used. The Viking ship was very long and slender, which gave it the ability to get into places most other ships could never get into. Much of Europe is connected by canals, which is how the Vikings were able to access Paris.