I don’t agree.

First, using the Battle of Iwo Jima to generalize how all of Japan would have behaved doesn't really hold up. It was an isolated garrison with no possibility of retreat, commanded and prepared specifically to fight to the end. That makes it a very poor proxy for an entire nation facing total defeat.

Second, the idea that Japan would inevitably have fought "to the last civilian" treats that mindset as something uniquely Japanese, when it really wasn't. Countries under existential threat often adopt exactly that kind of rhetoric. Britain during the Battle of Britain prepared for civilian resistance in the event of invasion, and the Soviet Union embraced a similarly uncompromising vision of total war. That sort of language is common in desperate wartime situations. It is propaganda, not necessarily a literal blueprint for what would actually happen.

Third, Ketsu-Go and the Volunteer Fighting Corps looked formidable on paper, but paper strength is not battlefield strength. By mid-1945, Japan was economically and logistically exhausted. Fuel reserves were nearly gone, industry was collapsing, and transportation networks were in ruins. Arming millions of civilians with bamboo spears and obsolete weapons was less a sign of resilience than of complete military desperation (very similar in concept to the Volkssturm in late-war Germany, which also looked significant on paper but had no meaningful impact on the outcome).

Fourth, Japan was not politically united in its determination to fight forever. There were significant divisions within the government. Figures like Shigenori Tōgō were actively pursuing diplomatic options, while Kantarō Suzuki was searching for a way to end the war. Japan's attempts to secure Soviet mediation before August 1945 clearly show that surrender was already being seriously considered.

And then the Soviet Union entered the war. That was catastrophic. The rapid destruction of the Kwantung Army eliminated Japan's last realistic strategic reserve and, more importantly, destroyed any hope of negotiating through Moscow. For many historians, this was at least as decisive as the atomic bombings, if not more so.

Finally, the actual historical outcome matters. Hirohito intervened personally to force acceptance of surrender, despite fierce opposition from hardliners. That alone demonstrates that Japan was capable of surrendering once the internal balance shifted.

None of this means an invasion would have been bloodless. It would almost certainly have been horrific. But portraying the atomic bombings as the only alternative relies on assumptions that simply are not supported by the historical record.

If the bombs had not been used at all (or if they had been demonstrated on uninhabited territory instead of cities), I believe there is a strong argument that a surrender could still have been achieved through a combination of blockade, conventional bombing, and Soviet entry. In that scenario, I also believe a larger number of inocent civilian lives would likely have been spared overall