Before there there was Hague Conventions of 1899 and 1907. Those were violated in WW1 on a large scale and no alternative had been put into place.
All these things are good and nice, but the reality is, if disagreeing with these is vital to win a war, literally no nation followed them.
Those kinds of agreements are good attempts in peace time to improve the chance of good outcomes, but in reality, in major global they are just pieces of papers that can not be enforced.
If you want to run around and simply say everybody is evil, then you can do that. But if you actually put yourself in the position of those people and try to make decisions if you want to be critical, explain what and how you would have done things differently.
And what cost would you have been willing to engage in to achieve that moral high ground.
They made it earlier in the war. Civilians were the war economy and civilians were legit targets for all nations in war.
Civilians in a total war are just not typical civilians. Everybody in society was mobilized for war.
> The very idea of thinking about the acts committed by your own side is strongly, strongly taboo.
No it isn't. Lots of historians work on that. There are lots of talks about it in places like WW2 History Museum and so on.