Operation Olympic or Nuke Hiroshima/Nagasaki
Operation Olympic was to seize the southern island of Kyushu in preparation to move on the main Japanese island of Honshu.
Allied casualty estimates range from 100,000 to 500,000 just for seizing the lower third of Kyushu.
Not only did Fat Man and Little Boy save countless Marine lives, they also saved Japanese civilian lives. A
Imperial Japanese Planner writes: But even the highest-ranking government were horrified at the Army's primitive notions for militia defense. In July 1945, Premier Suzuki and his associates were invited to visit an amazing display of weapons to be issued the Japanese citizenry: Single-shot, muzzle-loading muskets; longbows and arrows (effective range 30-40 meters, hit probability 50%, said the placards); bamboo spears; pitchforks.
After defeating the Imperial regulars, we would have had to slaughter old men and women. Perhaps an honorable death for them, but not an honorable task for Marines.
The Imperial Staff just would not quit. The destruction of Hiroshima and Nagasaki gave the Emperor his face saving excuse to capitulate.