Horrifying, but atrocities like this were known to have happened in quite a lot of places and were pretty much condoned by the Japanese high command. I'm also not sure what the HN specific angle is?
I believe the notion that states are driven to war by resources seeking, which can result simply from incompetent government, poor tax collection, or natural catastrophe. So global prosperity is the best deterrent to war.
The notion also guides which states you should assess are security or war threats -- the ones with that have economic capacity to meet their own growth, or the failed ones, with a large dissatisfied population easily roused to anger at a fabricated external scapegoat.
Genghis Khan neutralized his powerful competitors by making them rich. Perhaps, and this is possibly quite a reach, Japan's war mongering was driven quite a lot by its self-imposed trade isolation that depleted the state coffers, than by inherent expansionist rhetoric which was simply mobilized to motivate.
Economic prosperity and co-dependence is absolutely not a barrier to war. This line of thinking was an extremely popular explanation of why something like World War I couldn't happen.
And then it did,
This is assuming the definitions of resources line up. Some things that should be treated as a resource based on historic evidence of human behavior are not, thus they aren't included in global prosperity guidelines and thus the potential for them to create conflict and human right abuses (even if they don't escalate to war) persists even when optimizing for prosperity.
As an example, consider the gender disparity in China that is driving a massive and growing human trafficking problem despite an increase in prosperity.
The "left behind" (say the surplus of men in Vietnam, far greater than in China, in any case) are obviously unhappy about the situation and blaming "China" or "America" is an easy scapegoat, but the issues are less foreign and more domestic and economic.
It's always easier to blame foreigners, but looking within the country and taking responsibility is the only way to better the situation of its inhabitants. When emotive issues like sex and marriage are involved people understandably get confused and forget that.
A great positive for China is the equality of gender opportunity has created the situation where many hard working, intelligent women choose a career, business or personal focus over relationships.
And a female-heavy workforce is actually a boon for national security, and more men able to work more hours a boon for the economy. It's those other countries, those with many young and angry youth, but without the strong economies to put them to work, and easily angered by issues such as blaming foreign states, that are more security risks for creating war.
Regardless of the root cause, these tensions can give rise to issues that can push countries to war, or to the current day equivalent in this era of MAD.
WW2 is all atrocity. There was nothing noble about it. All sides pretended they were fighting to "save the world". The japanese claimed they were fighting to liberate asia from european colonizers. The germans claimed they were trying to save the world from soviets/etc. We claimed we were trying the world. It's all nonsense. Everyone was fighting over wealth and money.
Had the japanese won ww2, they would have framed it like they were trying to liberate australia from genocidal europen invaders oppressing the aborigines all the while raping the land for resources. Similar to what the british did to australia when they conquered it. Just like we pretend we "liberated" the philippines from the japanese when in actuality, we had invaded and colonized the philippines for 50 years before the japanese decided to play empire.
The point of ww2 should be that everyone is capable of and has committed evil and we shouldn't have another war like that. But of course the winning side gets to write the history and naturally, the winning side twists history to for their benefit. In japan's case, even the losing side twists it to their benefit.
As sherman said, "War is hell". There aren't any saints in hell.
The evidence shows that after the war, the Allies gave lots of money to their defeated enemies.