"in most locales wearing a mask in public is illegal unless it is part of a gala event"
The German during the Second World War [WW2] very innovative in the use of camouflage [camo] combat uniform. A variety of combat dress to include smocks, what appears to be an overall type of camo battle uniform, helmet covers, and even MASKS.
Conceal the face but not obstruct the vision the goal. NOT face paint but a MASK MASKS not to protect either against the cold but camouflage the goal!
An all encompassing camo uniform of various types of camouflage design, the basic form being called "splinter".
The Waffen SS seems to have been particularly fond of camo apparel, it also should be noted that camo battle dress HAD BEEN worn by other combatants prior to WW2, the German making a much more concerted effort at least to equip the combat troops with the latest and greatest.
Thanks to the Menschheit volkermord web site we have some interesting images of German troops during WW2 wearing face masks
This particular face mask would tend to obstruct the vision more than provide camouflage?
These troops wearing the Heer [German army] "splinter" face mask. Carrying at least that man in the foreground a Soviet sub-machine gun.