Yes, you’re right of course that WW2 is not "modern" in one sense, but I meant wars in which, unlike in the days before bomber planes, civilian areas can be easily targeted and attacks are not confined to battles between armies in battlefields or ships at sea, as in olden times.
Yes, I’m sure some of the tactics that were used in WW2 by the Allies as well as their enemies would be against the "rules" of modern warfare. Yet they helped defeat the Nazis, which was by no means a foregone conclusion. The trouble is that those who keep to the rules are often at a disadvantage against those who don’t. The Hamas cold-blooded massacre and rapes of civilians last October certainly broke all the "rules", but it doesn’t seem to have done them much harm in the opinions of a lot of people, does it? The abduction of hundreds of civilians was certainly against the "rules", but I’ve yet to see an international popular outcry demanding that they be released, or any penalty being suffered by Hamas for it.