[PeterPrinciple]

7,000,000 man, single blow attach against Japan planned. If we had gone this route, when would this have happened?

[Homer_J_Simpson]

Operation Downfall called for landings on Japan in November 1945 (Kyushu, Shikoku) and March 1946 (Honshu).

[AppyPappy]

The Japanese were ready to throw in the towel. The die-hards were starting to lose power and there were still a few leaders who thought they could bargain with us. They had already approached middle parties with thoughts of terms. The atom bombs just pushed them to move faster and give up the idea of terms.
They literally had nothing left.

[GeronL]

probably would have started by the end of the year and it would have been bloody

I can only imagine sea-borne assaults and landings in several Japanese cities at the same time.

[colorado tanker]

Operation Downfall had two components. Operation Olympic, set for November, was the invasion of Kyushu. The plan was to occupy the southern third of the island to provide airfields, logistics facilities and staging areas for the invasion of Honshu. Olympic was to have been staffed with troops already in the Pacific. There is some controversy what would have happened if Japan had not surrendered after the atomic bombs dropped. Intelligence is learning that the Japanese have correctly deduced that Kyushu is our next target and the Navy is becoming alarmed. The Japanese know our habit of never jumping farther than our land based air cover can extend. So, there might have been a rethink of that plan.

Coronet is the invasion of Honshu with landings near Tokyo. It was anticipated that the occupation of Tokyo and the Kanto Plain would force surrender, but if not there could have been further operations.

It is Coronet that the seven million man army will support. Those troops are almost all in transit or in training in the U.S. in July 1945. The 86th Division was the first to redeploy from Europe. They were slated for the Pacific and got amphibious training. When he Battle of the Bulge drove home the lack of a strategic reserve in Europe they were sent to the ETO. Because of their short time in combat in Europe and Pacific combat training, they were the first to go. According to Wiki they were in Phillipine waters when Japan surrendered.

Coronet was tentatively set for March 1, 1945, but obviously depended on progress in Olympic.

https://en.wikipedia.org/wiki/Operation_Downfall