For example Russia using its whole arsenal to create maximum chaos to create some opportunities, or North Korea invading South Korea. Pakistan, China and Iran could def. also be cooking something.
Might as well go balls to the wall now that the enemy is weakened and you have a lot less to lose. Especially if your economy is mostly self-sustained and doesn't rely on globalization to function properly.
(https://en.wikipedia.org/wiki/Nuclear_electromagnetic_pulse#...)
I think the question was more if any countries have ready made plans to exploit the natural disaster for military gain. Like does any country have a standing order to in the case of massive global disruption subdue or attack their geopolitical rivals?
So the hypothetical nation state here would need a ready-to-go plan ready to roll out at any time, and the plan must assume the native country also has all electronics knocked out along with the adversarial country. Such an all-out attack by itself would turn the world against this aggressor, moreso since it exploited the event and was premeditated. I think it's unlikely, it would be a crazy thing to do.
Now, who do I think might want to pull off something like this? A terrorist group could have a plan spooled up just waiting for this event. That, and I would expect some opportunists to appear as well.