Very poor choice because no matter how one tries to justify it, it was totally and completely illegal to attack whole cities of civilians.
There is no way to ever make that anything but a serious war crime, that sets an incredibly bad precedent.
You could almost justify attacking civilians in an democratic republic, where each individual is somewhat responsible for that the government does, but the civilians in imperial Japan were totally and completely innocent, since they had no part in starting the war.
You seem to forget the Nazi's. You also forget the Japanese attacks on multiple islands at the same time they attacked Pearl Harbor.
Civilians are frequently targeted in a war with the idea to demoralize the enemy.
The Nazi's were attacking Britain's military installations. A Nazi heavy bomber gets lost and accidentally bombs London. Churchill is understandably infuriated. Churchill orders the bombing of Berlin.
Shortly after the attack on Pearl Harbor came the surrender of the US on the peninsula of Bataan. That led to the Bataan Death march. Totally illegal.
Both Japan and the Nazi's had both brainwashed and threatened their soldiers and civilians that surrender or not fighting to the death was punishable by death. And, they meant it. With Japan, it was the Emporer who was, to them a religious figure, their god. The soldiers and civilians in the Philipines were so convinced of that horror and barbarism the American soldiers would unleash on them if they surrendered, many killed their children and committed suicide rather than be captured.
The Japanese citizenry of Japan was not armed with anything other than bamboo sharpened sticks and other weapons. The fear was not due to the Japanese being armed to the teeth with guns but rather that they would fight to the death, regardless of the casualties.
The Japanese were offered two opportunities to surrender, unconditionally. Japan refused both times. They conditioned their surrender on their Emperor in power. President Truman, demanding an unconditional surrender thus necessitating the A-Bomb being dropped on Hiroshima. Neither Hiroshima or Nagasaki were military targets. The US needed to make a point. The Japanese were offered another surrender after Hiroshima which they ignored, they never responded. After Nagasaki, the Japanese surrendered with the only condition that the Emporer would remain but as a figurehead only but with no powers. The Emporer cast the deciding vote.