The problem is how do you quickly spin up? You can't take an assembly line manufacturing a truck and turn it into manufacturing a tank. Well, you can, but it's basically you take the building it's in, throw away three fourths of the custom jigs and replace it with brand new custom jigs for a tank. I'm sure there's a small overlap of things you can use for both, but it wouldn't be very large.

Tanks are relatively easy to spin on production of. No nation ever started building a battleship in the time of war that then saw service in that war. Battleships commissioned during war had been started during peacetime or they were scrapped during the war because they didn't fit into the time or they were started under high holds, but they couldn't be finished in time. aircraft carriers are likely to be the same place going forward - you have to make them beforehand.

Things like artillery shells, which need to have the ability to quickly spin up production, but that's relatively easy to do. Which is why we're so low on production. The one thing that's lacking is the willpower to actually spin up production because as we quickly discover you could do it but that means all the things that your people are doing instead can't be done.

> I wonder if it wouldn't be better to have a Lowe level of constant military spending and have the ability and reputation to be able to quickly spin up and scale military production.

I think the issue is that you need different types of weapons for defence during peacetime and wartime (or when attacking).

For example, Stinger missiles are great for defending against the first wave of a drone attack or occasional rocket - they're effective and quick to use, but its immensely costly to maintain an arsenal of them that would last a year of sustained attack or even the production capability to replace used missiles. When you're under sustained attack it might be better to deploy more troops with lots of (previously warehoused) anti-aircraft cannon that can fill the sky with bullets for a few dollars to bring down drones and rockets and use your Stingers for those that get through.

Arguably, this has been the US’s strategy by constantly transitioning from one war to another for fifty years. Say what you will, but they’ve kept their war factories more busy than most.

We laugh at Russia's "fields of rusting armour" but one interpretation I saw somewhere said these scrap heaps were (plausibly) set up to be a source of components for whatever military requirements appeared next. It also kept the armaments industry ticking along for the last 80 years. The Japanese build two submarines every two years, by two companies. Unless they stuff up, each company can plan developments with forward looking. The contract system in the US has its drawbacks.

> have the ability and reputation to be able to quickly spin up and scale military production

Sure. How?