Yep! That's it! What are the prerequisites for someone to be regarded as war hero or condemned as war criminal?
Sorry, but this is only my opinion : it depends on whether side he/she is fighting for win or lose. If he/she (and
his/her side) wins, then he/she'll be considered hero. If he/she loses (defeated by their opponent), the opposite:
he (from now on only 'he'. Female war hero/criminal is rare) will almost possibly executed as war criminal.
Whether that person offended human rights, commited crime against humanity or of violated law of war seems to be later
consideration.
Why do I make this conclusion? Well, we all know that in WWII, the Allied won and the Axis lost. Soon, many Nazi officers (Heinrich Himmler, Hermann Goering, and ton others. Of course, if Hitler didn't die, he'll face the same fate) were executed, with reason of waging war, commiting war crimes and of course, genocide. Not only them, Japan's Tojo was also executed with waging war as main reason.
And now, the question is: What will happen if the Axis won? What will happen if German scientists were successful in creating first atomic bomb faster than Americas? If they use it in, say, London, Moscow, Manhattan (who knows? maybe Luftwaffe's morale would be lifted up?) or (Allied-controlled) Paris, I truly believe that the result will be very-very different! It's not impossible if the Axis won the war instead! And what would the Axis do toward their enemies' leaders? Well, it's not impossible if they would execute Churchill, Truman, or Stalin for the same reason: waging war. As for Stalin, I don't know if his "If you (soldiers) fall back, we will shoot you instead of them!" order can be considered as accusation. And never forget about what Soviets did to the captured Nazi soldiers.
Yet, Allied won after all. And what did they do to gain victory? One example: bombing, vary from carpet bombing to atomic bombing. The didn't only hit enemy soldier at the process, but also (and most are) civilians. I know the most possible answer is: "To prevent futhermore casualties." Toward whom? The invaders or the defenders? And what if the Axis won? They would probably use the same reason. The bombs killed the civilians. It's immoral.
As the conclusion: Final result of a war will decide who will be set as war criminal/hero. It's not (always) because of the cause, nor what they did during the war. It's more likely to something called Vengeance toward the losing sides' leaders.
And how about you all?