At or in

I have never heard of a country being in war, but they can certainly be at war, they can be involved in a war, they can be in a state of war, and they can wage war.

Additionally, a person can be in _a_ war, or even in _the_war, but I've never heard of a person being in war.

The only things I know of that can be in war are such things as everything ("all's fair in love and war"), types of people ("children are the real victims in war"), and other sort of abstract mentionings of war in general (e.g., "the role of airplanes in war").

It seems like a subject can be "at" some kind of noun without an article in certain cases, but cannot be "in" a noun without some sort of help.

Oh I don't know...prepositions are so odd anyway...

"Play at cards." - Ok.

"Plan in cards." - hmmm...I suppose a child might do this...especially if there were a lot of cards lying on the floor.

"Play at Chess." - OK.
"Play in Chess." - Not OK?
"Nation at war." - OK.
"Nation in war." - Not OK.
"Nation in wartime." - OK.
"Nation at wartime." - Not OK.
"House in flames." - OK.
"House at flames." - Not OK
"Man at leisure." - OK.
"Man in leisure." - Not OK?

in the second example above I did mean to put "play" not "plan"

'at' refers to a (rather abstract) state something is in: "at rest" "at play" "at war" "at full height" "at your leisure" "at lunch" "at "
vs.
'in' refers to an actual context or environment "in session", "inside" "in a war (zone)" "in the afternoon" "in ".

for ex, if you find yourself at war, you have an enemy, while if you find yourself in a war, you might not be a participant.

(note re below: one "plays chess" not 'at', or, "play at making/doing/etc...")

and then I suppose there are exceptions due to metaphors or usage, so "in heat" has become a state one is in, not just a warm place, etc.

Definitely "at war" -- and not "was" but "has been". "Was" means a condition that took place once and since ended. "Has been" means was and remains so now. So, "As far back as I remember the country has been at war."

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