When japan was attacked with nukes it was the WW2 the whole world was in tital Chaos, it was a colonial time, and finally US had a nuclear MONOPOLY.
Today world is anything but different, and the world, which has been firm and threatening against russia ( a super power) threat to use nuclear, will NEVET ALLOW ISRAEL TO USE NUKES.
israel will have to live with a nuclear regardless, no matter what they do: attack or no attack iran will get the bomb, which is pretty much a fait accompli now.