A heck of a lot of people &quot;doubted&quot; the bomb, in the sense that they weren&#x27;t <i>sure</i> smashing N Japanese cities would prompt them to surrender.  I&#x27;ve just finished <i>Now It Can Be Told</i>, published in 1962 by General Leslie Groves, who was in charge of the Manhattan Project, and from various things including how he praises one guy for his confidence that 2 would do it, it&#x27;s pretty clear even he wasn&#x27;t sure.<p>The excellent <i>Five Days in August</i> (<a href="http:&#x2F;&#x2F;www.amazon.com&#x2F;gp&#x2F;product&#x2F;0691168431&#x2F;" rel="nofollow">http:&#x2F;&#x2F;www.amazon.com&#x2F;gp&#x2F;product&#x2F;0691168431&#x2F;</a>) the author recommends comments how after Nagasaki there was quite a bit of discussion whether to use the 3rd bomb, which if I remember correctly was being constructed in Tinian at the time, for another strategic strike or to reserve it for tactical use in Operation Olympic, the invasion of Kyushuu projected to start in 3 months.  Which all but MacArthur had realized that absent the liberal use of nuclear or chemical was not going to happen, the Japanese had reinforced it too well, and had built too many kamikazis.