Well regulated militias all throughout history have always had minimum standards. The ancient greeks of the hoplite era that's not a warrior society i wouldn't consider it one a bunch of farmers but when the collective defense required it they put on armor and fought in phalanxes to protect their land. There are obvious differences between say your greek farmer hoplites and your viking warriors  in terms of the way they fight. ferocity fanaticism and fearlessness some combination of those things are commonly associated with the Vikings. If you're commanding a viking army against Romans or Chinese or steppe peoples or Alexander the Great's army you're going to think to yourself what I stand