9/11=terrorism?

The bombing of Hiroshima and Nagasaki killed at least 100000 civilians. These were not military targets. Japan was a military dictarorship at the time, the people had not elected the people in power and had no authority to sway them in any way, and therefore not responsible for any action that regime took.
They were not warned that their homes would be bombed by a weapon that their shelters could not protect them from.
How would you defend this without justifying the attack on WTC on 9/11?

"In 1945 Secretary of War Stimson, visiting my headquarters in Germany, informed me that our government was preparing to drop an atomic bomb on Japan. I was one of those who felt that there were a number of cogent reasons to question the wisdom of such an act. During his recitation of the relevant facts, I had been conscious of a feeling of depression and so I voiced to him my grave misgivings, first on the basis of my belief that Japan was already defeated and that dropping the bomb was completely unnecessary, and secondly because I thought that our country should avoid shocking world opinion by the use of a weapon whose employment was, I thought, no longer mandatory as a measure to save American lives."
-Dwight D Eisenhower