You are forgetting the fact that Japan was for the most part already defeated and on the path to surrender BEFORE THE BOMBS WERE DROPPED.
The U.S. dropped the bombs not to win the war, but to show them and the rest of the world (specifically Russia) who has the bigger dick.
"In 1945 Secretary of War Stimson, visiting my headquarters in Germany, informed me that our government was preparing to drop an atomic bomb on Japan. I was one of those who felt that there were a number of cogent reasons to question the wisdom of such an act. During his recitation of the relevant facts, I had been conscious of a feeling of depression and so I voiced to him my grave misgivings, first on the basis of my belief that Japan was already defeated and that dropping the bomb was completely unnecessary, and secondly because I thought that our country should avoid shocking world opinion by the use of a weapon whose employment was, I thought, no longer mandatory as a measure to save American lives."
~ General Dwight D. Eisenhower
"The Japanese had, in fact, already sued for peace the atomic bomb played no decisive part, from a purely military point of view, in the defeat of Japan."
~ Fleet Admiral Chester W. Nimitz, Commander in Chief of the U.S. Pacific Fleet
"The use of [the atomic bombs] at Hiroshima and Nagasaki was of no material assistance in our war against Japan. The Japanese were already defeated and ready to surrender."
~ Admiral William D. Leahy, Chief of Staff to President Truman
"Based on a detailed investigation of all the facts, and supported by the testimony of the surviving Japanese leaders involved, it is the Survey's opinion that certainly prior to 31 December 1945, and in all probability prior to 1 November 1945, Japan would have surrendered even if the atomic bombs had not been dropped, even if Russia had not entered the war, and even if no invasion had been planned or contemplated."
~ The United States Strategic Bombing Survey, after interviewing hundreds of Japanese civilian and military leaders after Japan surrendered
Face it, slaughtering thousands of innocent civilians INTENTIONALLY no matter what the justification is a crime against humanity.