Both of those books are excellent. Also, try Code-Name Downfall, by Norman Polmar and Thomas Allen. I've also got copies of the actual OLYMPIC and CORONET staff studies from MacArthur's HQ, along with CINCPAC Operations Plan 10-45 and Amphibious Forces Pacific Op Plan A11-45. Those, along with The Reports of General MacArthur, helped a lot when I did my MA Thesis on the planned invasion. One other point of interest: The US Strategic Bombing Survey concluded that if the invasion had gone ahead, the U.S. casualties in Kyushu would've been about 75,000. Higher than Normandy, but lower than the Bulge. As for CW use: British, Chinese and Soviet consent would've been required, as there was an inter-allied agreement on this, but I don't see the other Allies vetoing it. And a Soviet attack on Hokkaido? They didn't have the amphibious shipping needed to mount that operation, though Stalin wanted to do so. He was convinced by STAVKA to wait until Spring 1946, when shipping would presumably have been available. In any case, the Soviets in that brief Kuriles campaign got a taste of what the U.S. had experienced in the Central Pacific, and only the order to surrender on 15 Aug spared the Sovs from their own island-hopping campaign. They would've had to fight for each island from Kamchatka down to Hokkaido-against an enemy determined to fight to the death, as the Kuriles were considered to be Japanese soil like Okinawa was, so.....