Well, regardless of what Ike knew,
the Emperor of Japan knew that his war cabinette
was evenly divided between pacifists
and fanatics who demanded fighting to the death of the last grandmother.
Actually, the war faction had gotten to the point where they were willing to end the war in a draw, with a permanent ceasefire (somewhat like how the Korean War later ended).
The war faction had really expected that Okinawa was impregnable. And when we rolled right through it, it was quite a shock to their confidence.
Their idea after Okinawa was to get the Soviets to mediate peace talks, but in exchange for good relations with Japan after the war, the Soviets would secretly agree to mediate in bad faith, to Japan's advantage, allowing the war to end without Japan surrendering.
Japan was still attempting to discuss that plot with the Soviets when the Soviets declared war on them.
The Emperor was content to let the war faction pursue this strategy, but once the Soviet war declaration made the entire idea non-workable, that was when the Emperor diverged from the war faction.
The war faction's next idea was that they would repel our first attempt to invade the home islands, causing enough American casualties that we'd be demoralized and then agree to end the war in a draw. But the Emperor didn't buy it, and sided with the peace faction and ordered a surrender.
The entire "end the war in a draw" thing was pretty silly, because we'd have never agreed to it even if Japan had got the Soviets to help them. The only thing Japan really succeeded in doing was drawing out the war until they got nuked twice (though at least they ended the war before they got nuked a third time).
The military faction's last idea about repelling our invasion was also silly. We had broken their codes and knew of their huge buildup right in the path of Operation Downfall.
The war had ended before any concrete changes were made, but it seems clear that we were on the verge of scrapping Downfall and invading northern Honshu instead. Japan had little defenses there, and we'd have been able to fight our way down the coast to Tokyo.
The only real drawback would have been that we would not have had air cover from ground-based fighters because it was out of range. However, we would have started saving up A-bombs after dropping the third one on Tokyo, and we would have had about a dozen on hand to clear the beaches with just before our troops came ashore.
Indeed, on the night of August 14, 1945 Major Kenji Hatanaka
led troops successfully invading the Imperial Palace,
searching in vain for a recorded speech of the Emperor
declaring surrender to the Allies, in an effort to overthrow
the government and to continue fighting until annihilation.
This revolution persisted until about 6 AM of August 15, 1945,
the day when the Emperor's surrender speech was played over the radio at noon.
I wonder if Ike knew THAT.
The book "Japan's Longest Day," by The Pacific War Research Society, describes those events in great detail.
It's a worthwhile read if you haven't already read it.