Since when has any nation's national policy been guided by morality?
National policy is guided strictly by national interest. Countries, like people, always rationalize what's best for them to be what's best for everyone else.
Sometimes the national interest is served by moral actions, even a noble self-sacrifice, after all, being a good neighbor usually pays off in the long run, even from a strictly self-centered point of view. Likewise, unnecessary brutality and cruelty may have exactly the opposite effect one hopes it will, it may embolden your enemy, not intimidate him. But that is always a judgement call, and there is always a cost-benefit analysis.
Every attempt to make war easy and safe will result in humiliation and disaster.
War is cruelty. There is no use trying to reform it. The crueler it is, the sooner it will be over.
War is the remedy that our enemies have chosen, and I say let us give them all they want.
William Tecumseh Sherman