Norwegian guerrilla warfare

[Big Bad Voodoo]

At the same time the axe became a weapon of choice among Norwegian warriors, society collapsed and warfare became a free-for-all.

http://sciencenordic.com/norwegian-guerrilla-warfare-iron-age

[PersonFromPorlock]

Interesting, but it could be just that as the Roman economy collapsed and weapons became harder to secure, a tool/weapon like an axe was more useful to part-time marauders than a pure weapon like a sword. Barbarians need firewood, too.