This does not read like the investigative work of someone who has actually read any technical history on the subject. (The Making of the Atomic Bomb is probably the best scientific history ever written—I cannot recommend it highly enough.)
First, this totally fails to address the enormous industrial capacity required for enrichment of sufficient fissile material. It is implausible that 1943-1945 Japan could have achieved anything like this, regardless of technical expertise. The speculation of multiple stockpiled bombs and at least one test is far beyond feasible; even if they could have afforded the required scale of investment, the facilities and staff involved would be too large to have hidden: it likely would have required literally tens of percent of the entire Japanese industrial base over this period.
Second, the enriched uranium gun-based design (Little Boy) required more than 1000 tons of uranium oxide ore for the production of a single bomb, which is as much as the entire supply the author cites (maybe) reaching Japan.
Third, the speculation about bomber delivery seems extremely out of touch. Even the (much larger-capacity) B-29 required significant adaptation to deliver the 5-ton Mk 3 (Fat Man) and Little Boy, and, beyond mass, the designs could only barely fit within its fuselage dimensions.
Much more likely, all of the source reports were the result of rumors and misunderstandings. The most they could feasibly have built, tested, or hoped to deliver would have been small dirty bombs (a concept also well-known at the time). Perhaps they did, and this was the origin of the rumors; perhaps it was simply hearsay and speculation at a time of atomic fever.
First, this totally fails to address the enormous industrial capacity required for enrichment of sufficient fissile material. It is implausible that 1943-1945 Japan could have achieved anything like this, regardless of technical expertise. The speculation of multiple stockpiled bombs and at least one test is far beyond feasible; even if they could have afforded the required scale of investment, the facilities and staff involved would be too large to have hidden: it likely would have required literally tens of percent of the entire Japanese industrial base over this period.
Second, the enriched uranium gun-based design (Little Boy) required more than 1000 tons of uranium oxide ore for the production of a single bomb, which is as much as the entire supply the author cites (maybe) reaching Japan.
Third, the speculation about bomber delivery seems extremely out of touch. Even the (much larger-capacity) B-29 required significant adaptation to deliver the 5-ton Mk 3 (Fat Man) and Little Boy, and, beyond mass, the designs could only barely fit within its fuselage dimensions.
Much more likely, all of the source reports were the result of rumors and misunderstandings. The most they could feasibly have built, tested, or hoped to deliver would have been small dirty bombs (a concept also well-known at the time). Perhaps they did, and this was the origin of the rumors; perhaps it was simply hearsay and speculation at a time of atomic fever.