In 1945, the cities chosen as atomic targets were deliberately spared conventional bombing so planners could measure the weapons' effects on an undamaged city. This episode moves past the standard timeline to examine the grim mathematics, the secret debates, and the physics behind the decision.

We look at the projected cost of invading Japan, the two very different bomb designs, why a demonstration was rejected, the target committee's clinical criteria, the missions themselves, and the debate over necessity that continues today.

• Operation Downfall estimates and the manpower crisis of 1945
• The gun-type Little Boy and implosion-type Fat Man designs
• Why leaders rejected a non-combat demonstration of the weapon
• Radiation sickness and how ionizing radiation damages the body
• The Soviet invasion of Manchu ...