So even if copyright was shrunk to a single year, or less, that doesn't necessarily imply the immediate spread of next-generation military technology to one's neighbours.

I never said it did; I was speaking of material in general, such as civilian information - if it makes the economy grow faster, well, now they have more resources to spend on R&D themselves or to produce more of their existing arsenal or to buy more advanced weaponry from other countries.

If IP abolition did directly convey next-gen military tech to the neighboring country, that would be an even stronger argument against it, of course.