It’s hard to partially parse the sentence until the very end. If you remove the word “require”, then “mass” seems more likely to be an adjective, along the lines of “mass destruction” or “mass casualty”.
Inserting a “that” would help. …mass that inaccurate…
It is also challenging to produce and transport the mind-boggling mass THAT inaccurate weapons require.
The sheer mass of steel and explosives that have to run on railways to the Ukrainian front means inevitable shell-hunger. The war is being fought in a kind of slow-motion since materiel is the limiting reagent. I found the author's explanation helpful to find the wisdom in the fancy high-tech US path.
