When Japan was occupied by the US, scientists and military analysts found that nuclear fallout posed a major threat to people and animals. However, the persistence of the problem was not realized for several years. Radioactivity from fallout contributed to radiation sickness among the bomb survivors, with many suffering from cancer in their later years.
The devastation caused by the bombings led in part to a reluctance by political leaders to use nuclear weapons. Despite stockpiling and numerous close calls, no atomic bombs have been used in warfare since 1945.