I had rather guessed as much. I think you don't really understand the military application of cyber.No, I’m not confusing terms.
Quad super computers either aren't a thing or aren't very prominent. Quad core supercomputers are, but so what? They aren't magic - it's just extra computing power.
Encryption as a term is meaningless, and your statement that 'the fastest recorded breaking of encryption is 200s' is innacurate. Encryption comes in lots of forms, some popular forms of which (eg AES) are theoretically unbreakable on current computing power assumptions but could be cracked in future. They can be vulnerable to side-channel attacks, but that's not what you're talking about.
In your scenario, how are you getting the data from the enemy system and what's your mechanism to continue to get that data? How is that volume of data being egressed from the battlefield back to a site with a supercomputer (Cheltenham, presumably)? It's not just a computing power problem.