British officers planning trench raids in the front lines during WWI. Or, at least, that's where I've been told the expression originates.
Really, though, is it impossible to imagine no one, ever, using a cigarette pack to jot something down? It's a colloquialism. It doesn't even have to be taken literally to make sense. What is gained by questioning it on that level?
Wouldn't the back have printing on it? I could imagine someone ripping the pack open and writing on the insides, which are blank.
I took the OP's question to really be a question about the origin of that phrase, and with your answer, I learned something I didn't know before. So I, for one, am happy the question was asked.
The OP's question was clearly skeptical though:
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napkins, and envelopes at least kind of make sense.
Who was ever writing on the back of cigarette packs?
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Implication being that writing on the back of cig packs does not make sense. I'd agree with your reading if not for the "at least kind of make sense" bit.
in india.