I don't believe the record supports this view. Hiroshima and Nagasaki both contained military assets, which is why they were targeted, after a lengthy debate in which the extent of civilian casualties was a major consideration. If civilian deaths was the goal, the bombs would have been dropped on Tokyo, Osaka, or Kyoto, all with greater civilian populations. Kyoto, in particular, was not targeted because of humanitarian considerations.
Furthermore, I don't believe that heads of state can commit the crime of murder against the civilians of another nation with whom they are at war. Murder is a crime that exists only within the jurisdiction of the laws of a state, not between states.
Your views are those primarily adopted by 20th century pacifists, although you don't seem to be one yourself. They are not supported by the “laws of war,” such as they are, as they have been expounded since the 17th century.
Cruelty? I don't think I brought up the subject of cruelty. If you mean sadism, or the desire to inflict torture as revenge, or pleasure in others’ pain: no. I don’t know much about Truman’s sentiments, and his interior life cannot enter into my judgment, which to be just, must not rest on subjective states of mind, but on choices and acts.
But if you mean “choosing a target=city strategy in order to influence the elite with the shock and scope of the destruction,” then yes, he chose indiscriminate destruction as a means to an end. That is the moral objection.
There are countervailing elements (the civilians were told in a leaflet to evacuate, as they were in all the cities; in fact Hiroshima was full of evacuees from other cities. Very many cities had already been substantially destroyed. Where could they go? Nowhere. Could they go? Of course not); in the aftermath, measures were eventually taken to support people’s survival rather than their extermination); but that happened after the objective of unconditional surrender was gained; and that does not alter the choice of target=city as a means to an end.
”Furthermore, I don't believe that heads of state can commit the crime of murder against the civilians of another nation with whom they are at war. Murder is a crime that exists only within the jurisdiction of the laws of a state, not between states. “
This is an equivocation based on the idea that murder depends on legality. That is but one sub-definition, an illegal killing, and cannot be the major or decisive one: not after all the legal but unjust killings by states and their agents, as well as non-state actors in the 20 century. Murder is an unjust killing, and one classic way to kill unjustly is to fail to make a distinction between military targets and whole cities or extensive geographic areas, together with their populations.
I don’t know what you are referring to, when you say the "laws of war as they have been expounded since the 17th century” raise no objection to massacres. G.E.M. Anscombe of Oxford, who had scrutinized moral views of war since Aristotle and was considered an authority on the subject, said that the decision to kill an innocent person as a means to an end has been widely regarded as murder since classical antiquity, "and we pay tribute to these [concepts] by our moral indignation when our enemies violate them." (Anscombe said this in a famous 1958 essay criticizing Truman, and was neither a leftist nor a pacifist.)
I myself have never read any laws of states, international laws, or Natural Law philosophy which puts forward the idea that massacre of noncombatants is acceptable in time of war. It certainly violates Just War criteria since Vitoria (Renaissance). You’ll have to send me a link or quote me chapter and verse if you want to convince me otherwise.
Hey, I'm here to learn.
(And it's past my bedtime. Yikes. G'night.)