In my HRE campaign, I used to have a fair bunch of viking troops. Nearly a full stack of just landsmenn and some huscarles in Naples alone, waiting to be reassigned to several other stacks so as to balance all armies out a bit.

Then, the emperor (who, at the age of 63, had succeeded his brother who died at 65, because the latter's eldest son was only a kid, about 12 years old) died two years after his ascension to the throne, before his nephew had come of age. The count of Flanders was then elected emperor, but for some reason, probably some marriage I'd forgotten about, Naples was turned over to the Sicilians, along with all those vikings!



Now, I'm just waiting for the Sicilians to break our alliance to jump on those traitors with a big army and ride them down with lots and lots of mercenary heavy cavalry, putting an end to the viking era.