First only if you don't count minor details like Pearl Harbor. And given that we were systematically destroying their urban areas, just less efficiently albeit with more casualties, it's again a different thing.

The policy the above poster is referring to is No First Use [1], which is specifically about the use of nuclear weapons as a means of warfare. The Pearl Harbor attack, as it was not nuclear in nature, would not be relevant the No First Use policy if it were being followed to the letter and spirit.

How most nuclear powers would actually react to large-scale non-nuclear aggression is of course a whole different discussion.

1 - https://en.wikipedia.org/wiki/No_first_use

More efficiently.

Hiroshima and Nagasaki were not the most destructive bombing runs in WWII.

The March 9th 1945 bombings of Tokyo were far more destructive.