@blueoddog
Medieval warriors have long hair to act as additional layer of protection from being beheaded from behind. A braid made of hair is actually very good protection against bladed weapons, except for the heavier ones such as an axe or baldiche. Even if it's not braided, just loose strands of hair on the neck protects against sword strikes. There was even a mention that the muslim warriors were encouraged by their prophet to keep long hair as it helped protect their necks.
Medieval warriors also bundle up their long hair in their helmets to help cushion against the impact of blunt weapons such as maces or hammers. Without any cushioning, helms are deathtraps. Later medieval period had knights wear leather skullcap, under a chain coif, under a helm, but this is heavy and expensive. Prior to that, warriors would just use their own hair under the leather skullcap and iron cap and it worked fairly well with lighter burden on their heads and necks.