I don’t think there’s any particular nutritional benefit to eating a cooked meal hot vs. the same thing cold. But as you noted, there is a profound psychological benefit to eating a hot meal, and good food is probably the single most important thing when it comes to troop morale.
There certainly seems to be wide agreement that soldiers being able to have hot food improves morale. And one Confederate infantry unit, interrupted as they were trying to cook their first hot meal in several days, was said to have fought particularly ferociously (at Antietam, I think it was) because of their anger at the Union troops!
In Breaker Morant, the Bushveldt Carabineers help themselves to the hot coffee and food of the Boer guerillas they’ve just killed or driven off, and they’re glad to get it.
British armoured vehicles (including main battle tanks) all have a water boiling system built in. It’s considered necessary for the morale of the crew to be able to brew up under battle conditions. In addition to tea they can also prepare their hot rations using the boiling water.
a cold meal means that your body has to spend extra effort to warm the food to 98.6F as you chew/digest it, or else your core temperature lowers. On a cold day, this adds to discomfort. A hot meal does the reverse.
Cold meal tends also to imply some form of highly-concentrated and portable rations (hardtack, etc.) which don’t look and taste much like “real food.” While the hot meal might, itself, be made from preserved or ersatz stuff (powdered eggs, anyone?), perhaps it’s more evocative of the tastes and textures of “real food.”
Now I’ve got this mental image of a crew of Limeys in a tank, holding delicate porcelain teacups with their pinkies sticking out, while outside their armor, the chaos of war rages around them. “I say, sergeant, would you care for another scone?” <BOOM> “Jolly well, then, leftenant” <Pow Pow Pow>
There are vast quantities of quality food that are served room temperature to cold: sushi, california rolls, cheese, gazpacho (and other “quality” soups,) pate’, cucumber sandwiches (many sandwiches and wraps, for that matter,) many desserts. Not sure what you mean that “good types of food can’t be served cold.” Plus, I’ve had many horribly inedible meals that were hot.
I agree that there are plenty of great quality “cold” foods, but on the whole I have to go with some of the other posters in this thread, that psychologically, hot food implies quality food: hot food takes more time to prepare, meaning someone’s taken some time and effort to give you a good meal - which should make anyone feel good. I also wouldn’t discount the pure physical effect of eating something warm when the weather sucks.
All of those examples require refrigeration though. Can you think of anything that can be served at ambient temperature, that requires no refrigeration and is as comforting as a plate of bangers and mash with onion gravy?
Scones? Chocolate digestives and Hob-nobs are all we need, thank you very much!
Case in point: some years ago, the boyfriend of a housemate had just arrived home after a week away, literally just in the door and so his car was still full of his stuff, parked on the road. I was busy making tea for everyone. At this point, he spots a couple of kids smashing a window to get at his stuff, and chases after them, his girlfriend calling the police. My response? Get a couple of extra mugs out for the policemen.
Isn’t it fascinating how that happens to convert to precisely 37 C?