The military uses encryption that follows the same rules as other encryption.

They are generally more careful to make sure their crypto systems are secure. In theory.

The German military had a really good crypto system in WW2, and it was broken partly because humans made mistakes.

“Military grade” as in outsourced to the cheapest source and likely to be hugely overpriced when delivered?

These days, when it’s encrypted, a significant amount of time has to be put into decryption. So significant that the decrypted material will be irrelevant. (65 million years later, it doesn’t matter)