No, I’m not Greek. By defeating the Vikings, I mean ending the Viking raids that terrified Europe. This was not accomplished through force of arms on a battlefield (although Harold II of England did defeat a Viking invasion from Norway in 1066). Rather, it was accomplished through evangelism- the Norse people were converted to Christianity. Their conversion coincided with the end of those Viking raids. After that, the Norse became more involved in trade and commerce. The Hanseatic League is a good example.
You would probably be interested to know that the 1st Crusade was roughly one third Greek or Byzantine and one third Frankish (men from the Frankish successor states of France and the Holy Roman Empire). The rest came from areas controlled by the Norse, making nearly a third of the entire Crusade Viking.
Nope, you didn't quite Christianize all of them.