With regard to underwear being worn in kilted regiments, one of my friends was once Major and 2IC of the Black Watch of Canada (RHR), and he told me that at guard mounting, the RSM would inspect the troops. When he passed behind a rank, he would use his pace stick to lift the kilts and any man caught wearing underwear was fined $25. My friend further told me that in his regiment underwear with kilts was only allowed for bandsmen, pipers and drummers and regimental dancers. I think the famous 1990's photo of the Black Watch (RHR) soldiers performing a colors ceremony in Hong Kong before the turnover to the Chinese settled how that Regiment's regulations viewed the wearing of underwear!

With regard to comments here concerning uniformity in the military, I can only comment on my experiences in the U.S. Marine Corps. In general, if one was to go onboard a Marine base while I was on active duty (1960s - 1980s), there would be an amazing variety of uniforms being worn. You'd see Marines wearing Blue Dress (or variations), Service Greens (or variations), the combat utility uniform, airwing personnel in flight suits, plus all of these uniforms being worn with the green service sweater (wooley-pulley), jackets, raincoats or overcoats (depending on weather and season, and usually at the discretion of the wearer). Uniform "uniformity" was usually only enforced for Marines standing in formations. Today, most Marines on bases wear the seasonal camouflage utility uniform as "uniform of the day," so seeing the other unforms worn is unusual. But there are still variations with jackets, etc., usually at the discretion of individual Marines. Marines (and most troops) in the field are also allowed greater lattitude to arrange their uniforms for the sake of comfort or efficiency, and that has always been the case. When I was a grunt in Vietnam, we were issued green cotton "skivvy drawers" to wear under our jungle utilities, but after I tried them out, I dumped them and went without them. The skivvies would usually ball up like a knot in one's crotch and were uncomfortable, so they got tossed or were used as rags to clean weapons. Additionally, in one detached small unit I was in, we'd often go on patrol in t-shirts and soft covers rather then wear our utility jackets, helmets and flack jackets (we only wore those when officers or senior enlisted were around). Many of us also got rid of our cartridge belts and pouches and carried our magazines in over-the-shoulder claymore bags. Just some examples of how uniform regulations can be stretched by the troops, either with or without the endorsement of higher headquarters.