Idiots! War crimes are what the winners charge the losers with. It is not some term to be thrown around like it really had a moralistic meaning.
The Geneva Conventions are a farce that limit the actions of the aggrieved nation and lend protection to the aggressor.
We won WWII because we went to a TOTAL WAR of annihilation of our enemies. We were quite prepared to destroy the German and Japanese nations, cultures, and existence. They realized this and surrendered.
If you are not prepared to do this you have just decided to fight a war by rules laid down by your enemy. That is a recipe for losing a war as we did in Vietnam.
Civilians are part of the War Machine of your enemy. They harbor your enemy, they feed your enemy, they manufacture the weapons of war for your enemy. Total war is when one targets each and every part of society that supports your enemy.
If you are not willing to commit to TOTAL WAR, one would be advised not to go to war. You will probably lose. If your enemy knows you are prepared to go to TOTAL WAR, unless he is stronger than you, he will leave you in peace.