Helmets on Band of Brothers

[davver]

In the series Band of Brothers, why do they never do up their helmets? Did the American soldiers in WW2 do up their helmets? If not, why not?

[KebabMeister]

American helmets are like in two stages.  The inner helmet is like laminated material, almost like hardened hardboard/cardboard but shaped into helmet shape.  It has a canvas head support system so that your head isn't in direct contact with the actual helmet.  It's quite comfortable and holds the helmet firmly in place if it's a good fit.  Over the top of the 'light' helmet is the steel helmet.  This is much heavier and holds the lighter helmet even more in place!

So... I think that's why they don't need to do it up!

[Skids]

The helmet is suspended above your head, as KebabMeister says, however, under combat conditions its not exactly that stable that it'll stay on your head. These days, its normally worn with the chin-strap undone only during periods of calm where battle may be likely but the helmet may be removed and donned as required. It also makes you look cool if its undone.
During WWII both the Germans and the Americans had full cover helmets, whereas the British wore soup dishes. It was found by both the Germans and the Americans that if you snuck up on someone wearing a full-cover helmet, grabbed the front rim of the helmet from behind and gave a sharp tug backward, if the chin-strap was fastened, the back rim of the helmet would dig in to the back of the person's neck, and the neck would snap.
Hence, they took to not wearing the chin-strap fastened.

[Skids]

P.S. The U.S. Passive Armor System, Ground Troops (PASGT) helmet as used during Vietnam was in two peices; a laminated inner (with suspension assembly) and steel outer. The type used in WWII had the suspension assembly fixed directly to the steel pot.
The new helmets are made of ballistic Kevlar� and are also a single peice. They are also designed such that if the front rim is pulled backward the chin strap will slip off the chin resulting in strangulation, which is a bit better than having your neck snapped.