The "Knitting for Victory" group on Ravelry has been discussing what people knitted for the armed forces in Britain in World War II. I have come across an official booklet published in 1940 that sets out what type of garment was needed for the Army, with knitting instructions - and also what were not needed. I'm summarising the contents here partly for the benefit of that group.
The booklet specifies four acceptable garments: a cap-muffler, a sleeveless pullover, fingerless mittens extending beyond the wrist, and gum-boot stockings in oiled wool. The gum-boot stockings can be any colour, but the others should be khaki, or grey if that is unobtainable.
An obvious omission is a Balaclava helmet. You get the impression that every knitter in the country rushed into knitting those when war was declared - but the Army did not want them. The booklet explains why: the cap-muffler combines two different garments into one, and a soldier could not carry both a helmet and a cap. It also says that Balaclava helmets don't allow ear-phones to be adjusted in a hurry (by radio operators, presumably) - though the cap-muffler doesn't really solve that problem, it seems to me.
The booklet shows a cap-muffler in use. "A most useful two-in-one garment. Can be used as a cap and muffler, or a muffler alone. Comfortable to wear under steel helmet. Very easily knitted." (The model looks as though he has grown a moustache to disguise the fact that he's under-age - but perhaps that's me being old.)
Gloves, ordinary socks and pullovers with sleeves were not required because they were already being supplied - perhaps machine-knitted? Mittens, of the specified kind, were useful as well as gloves, for different purposes. A sleeveless pullover was felt to be "excellent for extra warmth and, being sleeveless, not too bulky under battle dress."
The booklet finishes by describing the working of the Voluntary Knitting Industry. A complex array of orgaizations had been set up to pass wool from the Wool Controller down to local working parties, and to collect together the knitted garments and eventually issue them to the troops. There was a huge clerical effort involved in recording everything, to ensure that the working parties could get wool at wholesale prices (and presumably also to ensure that all the wool issued was returned, knitted up.) Since the Government seem to have been perfectly capable of providing soldiers with most of their kit, I do wonder how necessary it was to use volunteer knitters at all, when it required such a huge (voluntary) effort to organize it all. Maybe one advantage was just to off-load some of the cost of clothing the Army to the civilian population - though I'm sure that the knitters also benefited by feeling that they were making a contribution to the war effort.