A more humane way to end the war IMO was to drop an atomic bomb on a military position or naval port which would have little civilian casualties, and then tell the Japanese that Tokyo would be destroyed next if they did not surrender that perhaps would have ended the war.

But it is very easy in 2023 to talk about what leaders in 1945 should have done. In August 1945 countries had just had more than a half decade of destroying each others cities and civilian populations already, and Truman was not going to risk the deaths of 100s of thousands of his troops to invade Japan. The Emperor would likely fought to the last man if not for the atomic bomb, based on historians judgement of the man.