For the last fifty years Iran has been "12 years away from acquiring nuclear weapons". Here's something to know - if a country is starting from ground zero, that county is 12 years away from acquiring nuclear weapons.
It took the Tube Alloys and Manhattan projects about six years, starting from the position of not even knowing that nuclear weapons were possible.
I reckon that any modern nation, knowing that nuclear weapons can be built, and starting only with the information currently freely available about the way they work, could build a fission bomb in a couple of years if they really wanted to.
H-Bombs are a bit trickier. But not a lot.
The real difficulty is making them small and light enough to be delivered to their targets by plane or missile. And that difficulty is readily overcome by unconventional delivery methods - you can get a shipping container delivered anywhere in the world in a couple of months, and most large cities are ports.
And none of these problems apply if you can just buy a warhead from Russia.
Twelve years? Only if they don't really want to do it, or have been infiltrated by saboteurs. Both likely apply in the case of Iran.
To be honest, stopping Iran from getting nukes is a mug's game. The smart move would be to stop them from wanting them; Or even smarter, from wanting to use them if, as, and when they get them.
Dropping bombs on them is unlikely to help with these goals.
