Nagasaki was a military city. Hiroshima was not. From wiki:
During World War II, at the time of the nuclear attack, Nagasaki was an important industrial city, containing both plants of the Mitsubishi Steel and Arms Works, the Akunoura Engine Works, Mitsubishi Arms Plant, Mitsubishi Electric Shipyards, Mitsubishi Steel and Arms Works.
Nagasaki was a military city. Hiroshima was not. From wiki:
During World War II, at the time of the nuclear attack, Nagasaki was an important industrial city, containing both plants of the Mitsubishi Steel and Arms Works, the Akunoura Engine Works, Mitsubishi Arms Plant, Mitsubishi Electric Shipyards, Mitsubishi Steel and Arms Works.