On May 5, 1945, the Japanese military launched a seaplane from a submarine off of the Oregon coast. That plane launched a balloon armed with a bomb. After the balloon deflated, a man and his five children approached the balloon and were killed by the bomb blast that was activated. Those civilians were the only American civilians to be killed within the continental United States by an axis attack during the war.
The exhibit showed how pregnant Japanese woman and women with children were effected by the radiation from the blast.
Hiroshima did eventually recover from the destruction caused by one of the atomic bombs to be dropped into the city at the end of World War II.