While he was proven wrong, his point was correct: WWI and WWII were economically disastrous to everyone involved except for the US. And in that case only because the US suffered no major damage to its infrastructure.
There's no way rational actors would start a war on the size of WWII. Only human insanity can cause another one. While that's no guarantee, it is still a strong preventative factor.
In the case of WW II the undamaged US was able to deploy its industrial capacity to "restart" the other industrial countries, first in Europe with the Marshall Plan and later subsidizing Japan as the "unsinkable aircraft carrier" to oppose the USSR during the Korean War. Eastern Europe and the USSR took longer to restart using their surviving industrial capacity.
In the event of a global conflict it is likely to go beyond the point where it is impossible to restart the current industrial system quickly enough to support existing levels of population. The population is now much more reliant on sophisticated technical systems for support and those technical systems are much more complex and fragile than in the 1940s. Consider how few major fabs costing 10s of billions are producing the lions share of semiconductors. Even fewer plants produce the capital equipment and critical reagents needed to reconstruct them and resume processing. The same is true for other supply chains.
I don’t think your second paragraph is quite right. Rational actors wouldn’t deliberately start such a war. But each act involved in starting it might be rational, while producing a profoundly irrational result.
I think WWI illustrates this well. Nobody set out to start a continent-wide war that would last for years. Nobody in charge of things was particularly crazy. Each act and response as the war kicked off was the sensible thing to do.
WWII is definitely showing off the opposite. Crazy person decides to conquer everything in sight, is eventually stopped.
Once the first step was taken, it wasn't long before WW1 became inevitable, as the huge chain of treaties and alliances kicked in, one by one.
WW2 might have been a much smaller affair had the world, or Versailles signatories been willing to enforce Versailles, German rearmament etc, and reacted after Germany started rearming (34), brought in conscription or re-militarised the Rhineland (36), by Anschluss (annexing Austria) in 38 it wouldn't have helped much. Ignoring everything, and the democracies being highly unwilling to rearm in step rather made WW2 inevitable too.
League of Nations ignoring Italian invasion of Ethiopia didn't help either.
And maybe a few of those economically disastrous wars are needed to empirically reinforce that theory.
I imagine that the future may look back at this era and marvel at how the US lost its world leading position through idiotic wars, while China bumbled its way to world leadership simply by not having any.
I think "bumbling" is a fair word to apply to a country that has ~20% of the population of the entire world, yet managed to avoid being a superpower for nearly the entire 20th century through idiotic self-inflicted wounds like the Cultural Revolution.
What policies do you regard as being intentionally instrumental to China's current success?
There are many ways to rationalize a war though, sure you can't take over others' resources without outright destroying them, but if your goal was to simply wipe a competitor out and monopolize a scarce resource, the picture changes.
The U.S. did very much benefit from the balance of power change that resulted from WWII. War determines who's left, not who's right. Eventually someone might try to be the one who is left.
It was not new to say that war was destructive. Angell's central thesis was that war was so destructive that nobody would dare start one, or if they did, that it would end quickly. That thesis was subsequently proven wrong multiple times.
Rational when considering economic theft across international borders. One cannot retrieve another countries GDP through launching a missile.
There is definitely a reason to start civil war internally though. Most of a nation's technological knowledge and economic worth is crystallized among masses of people yet the wealth generated by this knowledge is disproportionately concentrated among an elite few.
There is rational reason for this kind of war to be fought because such an attack on plutocrats does not destroy the economic value of a nation as it is not the plutocrats who hold such knowledge.
Even though there exists a rational reason for war to be waged based off of obscene wealth inequality I still believe it is unlikely to happen unless people start to starve.
There's no way rational actors would start a war on the size of WWII. Only human insanity can cause another one. While that's no guarantee, it is still a strong preventative factor.