Did Japan make an earnest attempt at a negotiated peace with the allies before the atomic bombings of Hiroshima and Nagasaki?

The Japanese Supreme War Council, which was essentially in charge of the country, was dominated by militarists who were not at all interested in a diplomatic end of the war prior to the events of August 6-9, 1945. There was, however, a minority "peace party," who, with some endorsement from the Emperor, was trying to see if there might be a route forward. Their method to do this was to try to approach the then-neutral Soviet Union with the hope that they would perhaps serve as a mediator between the US and Japan, and use that role to negotiate a conditional surrender.

The US was aware of these efforts because it had cracked Japanese diplomatic code. Their interpretation of them, essentially, was that it was pretty clear the Japanese weren't ready to accept unconditional surrender. Even the "peace party" wasn't pushing for that — they had conditions, at a minimum the preservation of the imperial house, but at times they seemed to think they might still have enough leverage to ask for more things, like the ability to hold on to some of the foreign territory they took in the war. And the US also was pretty aware that the "peace party" was a minority anyway, and hardly spoke for "Japan" as a whole.

The Japanese never even pitched this request directly to the Soviets; they danced around it. The Soviets had already committed themselves to declaring war against Japan in mid-August 1945, and were excited about the possibility of securing territorial concessions from that (like the entirety of Sakhalin Island and the Kuril Islands, which would give them easier access to the Pacific), so they had absolutely no interest or incentive to do what the Japanese wanted, but tried to avoid making that clear to the Japanese until they were ready to declare war against them. So the Soviets deliberately didn't really give the Japanese the opportunity to pitch their proposal, because they wanted to drag it all out until they were ready to attack. And, in fact, on the day that the Japanese ambassador to Moscow finally got his audience with Soviet foreign minister Molotov to pitch his plan, Molotov cut him off and told him that they were declaring war against Japan "the next day." That would have been bad enough, but by "the next day," he really meant within the next hour, because he didn't specify the time zone. Sneaky Soviets...

So by any reasonable measure, the Japanese absolutely did not make an earnest attempt at a negotiated peace. They can barely be considered to have make an exploratory attempt to set up the conditions for that negotiation, because, again, not only did they not actually present this proposal to the Soviets (or anyone else), they people making these "peace feelers" were not actually the ones fully in charge of Japan, and even if they had been successful at setting up a discussion there would have been no guarantees that the militarists would have gone along with it. So it was really quite preliminary.

This does not mean that these "feelers" were historically useless; they do give one a far more complicated view of the Japanese leadership's position on the war in the summer of 1945, and it is not quite as "fight to the death" as it is typically made out to be. But it was not an "earnest attempt" at a "negotiated peace." Even after the two atomic bombings and the Soviet declaration of war and invasion of Manchuria, the Japanese Supreme War Council still was not willing to accept an unconditional surrender until after their first conditional surrender offer had been rejected, US conventional bombing had increased, the military had put down an attempted coup from hardliners, and the Emperor himself personally intervened. Which is just to say, it was not like they had an "easy" time surrendering, even then. (The term used in one postwar report on this is "Japan's struggle to surrender," which I like as a way to phrase it.)

As for the ultimatum question — it depends on what you define as an ultimatum. After the Hiroshima bombing, the White House released a press release under Truman's name that proclaimed the attack to have been from an atomic bomb. It included the lines:

We are now prepared to obliterate more rapidly and completely every productive enterprise the Japanese have above ground in any city. We shall destroy their docks, their factories, and their communications. Let there be no mistake; we shall completely destroy Japan's power to make war.

It was to spare the Japanese people from utter destruction that the ultimatum of July 26 was issued at Potsdam. Their leaders promptly rejected that ultimatum. If they do not now accept our terms they may expect a rain of ruin from the air, the like of which has never been seen on this earth. Behind this air attack will follow sea and land forces in such numbers and power as they have not yet seen and with the fighting skill of which they are already well aware.

So the Japanese had this by August 7th, and the Nagasaki attack was not until August 9th. Does that count as an "ultimatum"? It seems pretty ultimatum-like to me. Now, I am not claiming that enough time was given between the two attacks. I do not think there was actually quite enough time, if the intent had been for them to confirm and process the news of Hiroshima and then act upon it. See here for a detailed timeline, and why "confirm and process" is a key term in the previous sentence (they reasonably needed to make sure it wasn't a bluff, and that took some time, and then they needed to meet to talk about it, and the news of the Nagasaki attack came to them during that meeting). The timing of the bombings was never about a strategic purpose like that, though; it was due to weather conditions. So if the author is suggesting that dropping another atomic bomb so soon was inappropriate if the goal was to avoid more bloodshed, I agree. That was not the goal, though, for better or worse. But he is wrong to say there was no further "ultimatum," in my view.

As for the essay, I have never heard of it before. Glancing at it very quickly, it seems like a standard British anti-atomic bomb take from the mid-1950s. I would not rely on it for historical details of the bombings themselves; we have much better research and sources since then. One can have complex views on the atomic bombs, and even suggest there were viable alternatives to it, without subscribing to old myths. That being said, one can certainly look at such an essay as a historical source of its time, and its core ethical question — is it OK to kill innocents in the prosecution of a greater cause? — is one that definitely should be debated today (and using the "atomic bombing decision" as a way to think about that is quite common, although quite fraught, because much of the history that people think they know about that is false — there was no "decision," it was not a simple choice of "bomb vs. invade," etc.). The way I prefer to phrase the core ethical question is: under what conditions is it a moral act for states to deliberately massacre hundreds of thousands of non-combatants? The answer doesn't have to be "no conditions," but it surely is not, "all conditions."

For more on the question of the Japanese peace feelers, I have written quite a bit on them here. For more on the difference between what most people think about the atomic bombings and what historians have found, see this other post which is directed at journalists but only because they have a major role in how the general public understands this stuff.