This grim and painstaking analysis of plans for operations Olympic and Coronet (the invasions of Kyushu and Honshu) argues that dropping atomic bombs on Hiroshima and Nagasaki was a military necessity that hastened the end of WW II and saved possibly millions of Japanese and American lives. Military experts Allen and Polmar (Merchants of Treason, 1988, etc.) build a persuasive case. Though Japanese forces had not won an engagement with the US since the war's first months, and defeat looked increasingly inevitable, the leaders of imperial Japan repeatedly vowed to fight US forces to the last man, woman, and child. The islands of Iwo Jima and Okinawa, not nearly as well defended as the Japanese home islands, had to be conquered in savage battles that lasted months and resulted in tens of thousands of American casualties. Allied demands for unconditional surrender were not an obstacle to peace, the authors argue; Americans were willing to permit Japan to retain the imperial system and to go on with its normal national life, but Japanese leaders rejected the offer. The morale and zeal of ordinary citizens to carry on the fight were high, even after American firebombings that claimed more lives than the atomic bombs would. The authors describe Olympic and Coronet in ghastly detail, noting that they might have resulted in more than 500,000 American casualties, as well as in the use of chemical and biological weapons by both sides. They conclude that, in making the decision to drop the atomic bombs, ""Truman was looking for ways to end the conflict honorably and at the lowest possible cost in American and Japanese lives."" (For another look at this period, see Stanley Weintraub, The Last Great Victory, p. 624.) The authors' masterful marshalling of the evidence prompts relief that the invasion of Japan never took place, but it's unlikely to put to rest historical speculation about the morality of Truman's decision.