The atomic bombings of Hiroshima and Nagasaki, 75 years ago on Thursday and Sunday respectively, are viewed with horror and regret. But do not using the atomic bomb would have been much worse. The total number of Japanese deaths attributed to the two bombs is estimated to be between 129,000 and 226,000. A US government report from July 1945 estimated that the invasion of the Japanese islands would cost between 5 and 10 million Japanese lives.

The American landing, scheduled for November 1, 1945, was to be considerably larger than the 1944 Normandy landing in Europe. More than 156,000 Allied soldiers disembarked on D-Day. They suffered more than 10,000 casualties, including 4,400 killed in action. They faced 50,000 German soldiers. The invasion of Japan is said to have involved some 766,000 Allied troops.

And it would have been harder than D-Day, which took the Germans by surprise. The Japanese had deduced both the approximate landing date (end of October) and the landing beaches on Kyushu, the southernmost of Japan’s main islands.

It was only after the war that the United States discovered the extent of Japan’s preparedness to defend against invasion. In June 1945, American intelligence estimated that 350,000 Japanese soldiers would defend Kyushu. After the Japanese surrendered, the US military demobilized some 784,000 men on Kyushu. In addition, there were some 575,000 Kyushu Internal Defense Forces. Unlike the 3: 1 ratio between allies and adversaries in Normandy, Japanese defenders would have outnumbered Allied troops during the initial assault landing.

The Japanese were also preparing more than 10,000 planes to launch suicide attacks against American landing ships before they could unload their troops. And Japan still had nearly five million soldiers and sailors still fighting in Taiwan, Korea, China, Manchuria and various Pacific islands.