All of the following have been cited as reasons for the dropping of atomic bombs on japan in 1945 except the need to block a planned japanese invasion of the united states block a planned japanese invasion of the united states keep the soviet union out of the war against japan keep the soviet union out of the war against japan save american lives save american lives demonstrate american superiority in weaponry to the soviet union demonstrate american superiority in weaponry to the soviet union force the unconditional surrender of japan