I just watched the 4 part series on Netflix called Tokyo Trial about the Tokyo War Crimes trial.
It is amazing but in this one, almost half of the judges dissented in some way, particularly on the topic of waging aggressive war! The dissenting judges claimed that condemning aggressive war as criminal involved either an ex post facto law and/or a lack of clear criteria to identify it, given that previous international agreements had said that each nation had the right to decide for itself what actions were aggressive or in self defense!
Now you might think that it is all cut and dried as to aggressve war, but the problem is that a lot of us live in the USA, and a lot of others believe that the 2nd war against Iraq constituted a war of aggression, forbidden by the UN charter and international law, and the USA contributed to that view by withdrawing from the agreements creating the ICC in 2002 and also, abandoning the attempt to get a 2nd UN resolution about the need to invade Iraq.
There is the movie Official Secrets which implies that that the UK abandoned a prosecution of an alleged spy or whistleblower, cause they would have had to admit that their own lawyers regarded the war in Iraq as a war of aggression!
So it is easy to say in retrospect that Germany and Japan were creating wars of aggression against Poland, China, etc, but I am also a guy living in the USA and I think that the war against Iraq was done, knowingly or negligently, under false pretenses.
Anyway, even the majority judges in the Tokyo Trial recognized that there was a serious question about the law against aggressive war as they were understanding it, and so, they gave some death penalty to those who did or commanded troops of atrocities, but they refrained from giving death to those who convicted of being a part of the gov while it was waging aggressive war.
Although WWII seems obvious, in most respects, in terms of right and wrong, Nuremberg, Tokyo and the US bombing of some civilians all raise difficult questions, impossible questions perhaps, for a person seeking to apply right and wrong (and the laws of God and the universe), I think.
In order to accomplish what people believed just at Nuremberg, “we,” meaning the Allies, disregarded the legal principles against ex post facto laws, or so some allege, even Western justices.
Oh, I sympathize with the dissenters, and I am not pro either side in terms of just war theory and international law. Yes, the Allies won as a part of bringing or restoring civilization, but the Allies also, it is alleged and appears, engaged in injustice along the way!