Between 1860 and 1916, every British soldier was supposed to have a mustache.It had to do with the idea of "masculinity".
the regulation was stopped in 1916 because the mustache got in the way of a tight fit of the gas mask: The same reason that short hair, only a small mustache, and no beards were the rule in the US Army.
When I read the Obama Army says beards are okay for "religious" reasons, or special hats, it makes me wonder how they get around the reality of helmet and gas mask protection. But never mind: Political correctness trumps all.
on the other hand we read this:
It is also still extremely common for British soldiers in Afghanistan to wear beards, as facial hair is still associated with power and authority in many Islamic regions.
Addendum: in the saga of the Bunnt Njal, one of the insults used in the fight was that he didn't have facial hair, i.e. that he was impotent or gay (despite having a wife and a couple sons). Which is why to read old literature you need footnotes...