Chambers Dictionary of Etymology says it was coined in 1862, is American English from Latin and refers to the American Civil War.
It's possible individual writers may have used it of other wars, but I have certainly never heard it used of any other. Possibly the OED has come across American writers using it. I've never read any American histories of WWII, so wouldn't have come across it.
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It's possible individual writers may have used it of other wars, but I have certainly never heard it used of any other. Possibly the OED has come across American writers using it. I've never read any American histories of WWII, so wouldn't have come across it.