The Japanese government plans a fanatical defence of Japan's home islands to the last man, woman and child
In April 1945, the Japanese Suzuki government had prepared a war policy called Ketsugo which was a refinement of the Shosango victory plan for the defence of the home islands to the last man. These plans would prepare the Japanese people psychologically to die as a nation in defence of their homeland. Even children, including girls, would be trained to use makeshift lethal weapons, and exhorted to sacrifice themselves by killing an American invader. To implement this policy of training children to kill, soldiers attended Japanese schools and trained even small children in the use of weapons such as bamboo spears.
The American government was aware from intelligence intercepts of the chilling implications of these Japanese defensive plans. Intelligence reports indicated that the Japanese would probably be able to muster two million troops and eight thousand aircraft for the defence of the four home islands against a traditional amphibious invasion. The dispersal of these military resources across Japan, and their careful concealment, would provide the Americans with no opportunity to destroy them from the air. The Ketsugo policy placed heavy reliance on suicide attacks on the American troops and their covering warships. For this purpose, several thousand aircraft would be adapted for suicide attacks. Other methods of suicide attack being developed included dynamite-filled "crash boats", guided human torpedoes, guided human rocket bombs (similar to the "Baka" rocket plane used against American ships at Okinawa), and specially trained ground suicide units carrying explosives. In addition, the invading Americans would have to face a civilian population drilled in guerilla tactics.
The Americans had every reason to be deeply disturbed when they learned about Japanese plans to defend the home islands by massive suicide attacks on American amphibious forces. The Kamikaze suicide attacks on Allied ships at Okinawa had alone produced a horrifying toll:
34 Allied warships sunk ;
368 Allied ships damaged (some fit only for scrap);
4,900 Allied sailors killed; and
4,874 Allied sailors wounded.
President Truman's military advisers warn him of the very high cost of an invasion of Japan
Faced with this knowledge of Japan's extraordinary plan to defend its home islands to the death, and the fanatical character of Japanese soldiers, and extrapolating the fanatical defence of Iwo Jima and Okinawa to an amphibious assault on Japan's four home islands, American military leaders were deeply concerned. They advised President Truman that an attempt to invade and subdue the Japanese on their home islands was likely to cost at least 1,000,000 American battle casualties.