I’m still in the mind set I guess of the “how many bullets” thread I started recently.
But I’m sure most of you have heard or read this portentious statement in the header. How the heck do they figure “all the firepower” (I think that’s the word they use), of a war?
Well you can total up all of the explosives (and maybe gunpowder and propellants) used in the war. The energy released in a nuclear explosion is commonly compared to the equivalent weight of TNT that has the same energy. The biggest nuclear explosion, Tsar Bomba, had a yield of 50 megatons – equivalent to the explosion you’d get if you piled 50 million tons of TNT all together and set it off.
The various militaries involved will have records of how much ordnance was produced, how it was used, and how much was left in stockpiles at the end of the war. That should allow them to at least estimate the amount of ordnance that was used in the entire war.
Typically the actual thing you’ll see doesn’t say “all the firepower,” but “[more than] all the bombs dropped in WWII,” or somesuch. Air forces kept pretty good records of ordnance dropped on various missions, and the total bombweights were added up long ago and used for strategic calculations as well as bragging rights, so it’s easy to look up this number and compare it to the megatonnage or kilotonnage of the weapon system to which you are comparing it.
edit: also air forces as a generalization tended to have bases behind the lines and were less frequently overrun than, say, infantry units; thus the records of air forces have a somewhat better chance at surviving the war intact.