Yes, maoists in China created a detailed invasion plan for the US to invade Canada, infiltrated the US government and then had them "declassified" in 1974 in order to create a mild temporary tension between the two close knit NATO allies.
Yeah, in the 1920's to boot. If B-movie (or nowadays just any movie studio) were on here, they'd take what you just wrote, add time travel to it and make it into a movie without giving you credit. And they'd probably find some way to use AI in it too.
I like how people forget that almost every countries military has plans to invade/defend their neighbourhood, better to have plans ready for that time then not having any plan.
Why would it be? It's always good to have contingency plans. This became even more clear in the 30s when political instability was rife everywhere. Never knew what your neighbors were going to do in a decade.