Why was it difficult to determine the exact death toll from the atomic bombings?

Determining the exact death toll from the atomic bombings of Hiroshima and Nagasaki was difficult because early efforts to quantify the casualties were necessarily estimates that often omitted significant population groups. Most notably, these initial counts failed to include thousands of Korean forced laborers who were present in both cities at the time of the attacks.1

Furthermore, the scale of the destruction hindered accurate record-keeping. The bombings decimated local infrastructure, including hospitals, firefighting stations, and communication lines, while killing or injuring the vast majority of medical personnel and emergency responders. Because the effects of the bombs—ranging from immediate blast injuries and burns to long-term radiation sickness, cancer, and related diseases—occurred over varying timeframes, it remained challenging to attribute every death directly to the initial event. Consequently, while official reports provided casualty figures, these numbers remained estimates rather than precise counts.123