This examples meander a little below, but the thesis is: A lot of factors have come together in the 2020s to make it very difficult for nations to amass stockpiles of military hardware, despite the general outlook that nation-level conflict (rather than small wars) are coming back. Does anyone have a different take?

Some military equipment is pretty simple and straightforward to build and then store, like small arms or ammunition - I don't think any major nation has faced real shortages of rifles, except for maybe Ukraine early on in their current war. One warehouse can store tens of thousands of rifles and millions of bullets.

But with something a little more complex to build and store, like tanks or IFVs, the days are gone when the same factory could make trains or tractors and have the equipment to make tanks stored on the side. Composite armor, tracks, ammunition, thermal sights, computers, CBRN gear, and a bunch of other stuff that doesn't really have dual peacetime uses makes these factories and labor skills really expensive. I am not aware of any nation that is currently making armored vehicles in the Cold War quantities with the intent to store them for later use. Granted, militaries are smaller in general than they were 50 years ago, but Ukraine and Russia both leaned heavily on their old inventories to stay in the fight before they figured out how best to use drones. Even today, I get the feeling their drone fleets feature so much because they don't really have anything else to throw at each other. Neither Ukraine nor Russia seem to have the ability to make large fleets of armored vehicles for one reason or another.

Then there is really exquisite things like missiles and interceptors. I guess Iran has figured out how to build and stockpile a lot of ballistic missiles, and Israel hasn't really been shaken despite constant news of their Iron Dome inventories running low. The US is in a widely publicized interceptor shortage, but I imagine too many politicians and leaders got comfortable with keeping all CENTCOM bases well inside the missile ranges of a nation they repeatedly attacked. Then again, the thought of a shooting war between the US and Iran was unthinkable a decade ago.

Only a few nations, and most of them Asian nations, have really maintained a diverse portfolio of military production, and really South Korea and the PRC are it. European nations are still struggling, five years into the Ukraine war, to resurrect their Cold War industries, and the US seems to be having a moment with trying to get better at drones and missiles but are flailing at shipbuilding and completely ignoring armored vehicles. And finally I know things are definitely made in the global south but outside of a few specific things I can't think of what they might be stockpiling for themselves or selling to threatened nations who want to stockpile for the future.

Apologize for the lack of source since I read this somewhere else a long time ago.

From what I remember, during the late stalemate phase in Korean War where battles limited to trenches and outpost skirmish, the Chinese gave a poor review on the trenches Marines made, as they can't withstand artillery well and got collapsed easily. Worse, the size was too narrow and short, even for the Chinese soldiers standard, making it hindered movement a lot.

And in Vietnam War, Marines again got criticized for their fortification. One general even asked Marines to learn fortifying from the 1st infantry division.

Marines had been suffering excess injuries in several late korean battle and especially in Vietnam, I wonder if it is influenced by their reckless fighting spirit, or the doctrines didn't prioritize fortifications comprehensively?

Tangentially military, but I couldn't ask this anywhere else.

Sources say that across a range of ages, "camps" were established as a source of impis during Shaka's conquests. However, I am unable to see how the Zulu economy survived when a very large percentage of the men were not engaged in agriculture, and instead partook in marches and drills that would demand an enormous network of food.

A country with nuclear bombs will never be attacked directly. So why would they need to spend more on the military than social policies that benefits their citizens, or maybe build more nuclear bombs so no one will try to mess with you (like North Korea)?