It is not valid as a synonym for torture and murder. The second factor to be noted is the inability under international law of any government to remove from its nationals their human rights and, it must follow, their rights to reparation when those human rights are violated. The victims of Japanese barbarism have insisted on this since the details of the peace treaty were published, and the passage of half a century has diminished neither the wrongs that were done to them nor the justice of their cause. The allies dropped nuclear weapons on Hiroshima and Nagasaki. Those acts were war crimes.
All war is cruel, but there are different levels of cruelty.
International law recognises the right of a country to fight a war in defence of its interests, but international law has established how such wars should be conducted. At the first level, where war, even nuclear war, is fought in accordance with the principles of international law, unnecessary violence, which means violence which does not contribute directly to the prosecution of the war, is carefully avoided. At the second level cruelty is used as a weapon of war, often to create and exploit terror among the civilian population. Obvious examples are the atrocities committed in Bosnia, and Stalin's order to the Red Army to humiliate German womanhood, but examples are common too in low intensity conflict, especially among terrorists active in advanced Western countries. At the third level cruelty is inflicted arbitrarily, not in pursuit of victory, but to amuse bored soldiers or to gratify their sadism.