The point is that the Japanese were willing to negotiate surrender terms. Vice President Harry Truman was a rube senator from Missouri and didn't have a freaking clue when he woke up one morning in April 1945 and found out that he was president. The generals were running the war and Truman was in it for the ride. FDR might not have been in his right mind when he decreed that the U.S. would accept nothing but unconditional surrender and that's what Truman accepted.There is a difference between "negotiating a surrender" and "dictating a cease fire".
And it can be seen quite clearly in that they outright rejected Potsdam, and refuse to consider or discuss it.
If they had honestly been willing to surrender, then at that time they would have opened a dialogue with the Allies. Either directly, or indirectly through a third party. But they did none of that, they openly and publicly dismissed it, even using the word "Mokusatsu", which normally translates to "kill with silence" (but also "treat with silent contempt").
That is because they felt they still had the upper hand in the war. That they were the stronger nation, and had the right and power to dictate terms. And not for a surrender, but an armistice to stop the fighting.
And remember, even Ambassador Soto was urging them constantly to "get serious" about ending the war, before it was too late. We actually have three records of all of their dispatches back and forth. Both those translated via Magic, those from Venona, then again from the Japanese archives themselves.
Nuclear Files: Library: Correspondence: Telegrams: Togo-Sato
Japanese Peace feelers in the Soviet Unionwww.nuclearfiles.org
I suggest anybody that wants to know how the final two months of the war were from the Japanese perspective read those dispatches.
Dispatch from Ambassador Soto to Foreign Minister Togo, 12 July 1945
No, the Big Six still had it in their minds that they could and would win the war, and had no intention of ending the war unless it was in their favor. And the Allied Powers would never have accepted that.
I find it fascinating that even today, people constantly try to "Monday morning quarterback" the negotiations, and say that Japan thought the Soviets were going to help them negotiate a peace. Here we have their own Ambassador telling them that would not happen, way back on 12 July. He knew the reality of it, and over and over tried to tell Tokyo that it would never happen unless Japan was ready to give major concessions. That only a surrender and not an armistice would end the war.
There is a reason why I constantly encourage people to go to the source documents, and not simply rely upon what others say. Those original documents give a direct peek into exactly was going on, unshaded and without spin. Japan had absolutely no idea we were "reading their mail", and what we see in the Soto-Togo messages was a lot of frustration, and demands to make the Soviets see things the way Japan wanted them to, and to do what they asked.