You assume that invasion would have been necessary.Why was invasion necessary? Without a Navy or Air Force, and having retreated to their own islands, what danger did Japan still present? The demand for Unconditional Surrender was not about saving American lives, but about the public's demand for revenge. In short, the use of nuclear weapons was a public relations decision, not a strategic decision.
Are you are aware that that Catholic morality has never permitted immoral acts in order for "good" to occur? You are free to justify these bombings all you like, but please refrain from improperly using Catholic teachings to make your case.
Many reasons: the American public was weary of war, and would not have tolerated a protracted wait for Japan to surrender; the Soviets were threatening to invade and occupy Hokkaidō, which would have led to a Korea-type standoff with the USSR (and probably another war); the militarist clique in Tokyo had to be completely subjugated to ensure a peaceful occupation; and for other reasons.
Plus they were all starving. The militarists in Tokyo could have held out for years. Meanwhile, millions of civilians would have literally starved to death.
Without a Navy or Air Force, and having retreated to their own islands, what danger did Japan still present?
Your knowledge of history is poor. Japan still had viable forces overseas (e.g. Korea and Manchuria) in August of 1945. According to Theodore F. Cook in Japan at War: An Oral History (1992), page 403, 3,527,000 Japanese military personnel were stationed outside of Japan at the time of surrender, with a further 4,335,500 in Japan, not including armed civilian auxiliaries.
The demand for Unconditional Surrender was not about saving American lives, but about the public's demand for revenge.
I disagree. The goal was to end the war as quickly as possible. If revenge had been the government's motive, we would have simply let the Japanese starve to death.
In short, the use of nuclear weapons was a public relations decision, not a strategic decision.
I disagree. It was intended as a veiled warning to Stalin, I suppose.
Are you are aware that that Catholic morality has never permitted immoral acts in order for "good" to occur?
Yes. For a Catholic, the end can never justify the means. Unfortunately, sometimes there is no choice but to use evil means in order to attain good ends. In such cases, those who employ the evil means should submit their acts to the judgment of Caesar and God. That's not fair, but that is reality.
You are free to justify these bombings all you like, but please refrain from improperly using Catholic teachings to make your case.
I'm not justifying anything. As I clearly and plainly said, the mass firebombing and nuclear attacks on Japan were immoral. All other options were immoral as well. Sometimes, good men are forced to make decisions in situations where no moral option exists. This is the tragedy of war.
Please re-read my post for comprehension.