Actually, there are ethics and morality that pertain to the waging of war.There is no morality in war, other than evil must be defeated.
To use an extreme example: let’s say that there is an orphanage with 1000 disabled infants in it. If you annihilate the orphanage, you will horrify the enemy so much with your ability to wage war that they will sue for peace. This is an example of an immoral means to a just end, the surrender of the enemy. You can’t do it.