Centerfield

I don’t see how deterrence would work today’s world. Our intelligence agencies have been proven to be indecisive at best and wrong more often than right. That doesn’t inspire the confidence necessary to condemn thousands of civilians to death. There would be a time period between the event, and when we had enough information to know where the material and financing originated. Do you believe a month after an attack congress would authorize a nuclear response over a conventional one?
If we had gotten into a shooting war with the USSR, and they used a tactical nuke (submarine or aircraft launched) to destroy a battle group would we have launched a strategic nuke at Moscow?
Today, if North Korea finances a nuclear weapon exploded on a ship near the coast of Japan, which city do you believe we would destroy? Would we limit the retaliation to one city? How would China respond? We have the ability to take North Korea with conventional troops, it would be costly but we could do it. Is it justifiable to use a nuke instead?
Nuclear deterrence only works in a few situations. If China were behind the attack, the situation changes and you may be right since we don’t have the ability to quickly remove the threat with conventional force. Deterrence is needed to eliminate some threats, but it’s not a viable option for dealing with rogue states or non-state actors.

Pointing out the obvious consequences of actions is not a deterrent. Any country with even mildly competent leadership realizes that helping terrorists launch a WMD attack against us, and us finding out, will result in their destruction. At least, I hope that would be our response. But in any event, any country that would do so would accept those consequences beforehand.

I believe our deterrent should be that if a WMD attack is ever successfully committed against us, then we will cripple the Muslim world to greatest extent possible. We need people and countries the terrorists don't want to destroy to have a stake in preventing any such attacks. Hopefully even the terrorists will agree that tens or hundreds of thousands of dead Americans aren't worth tens or hundreds of millions of Muslims.

The challenge comes when the terrorists either believe that it is fine to make involuntary martyrs to their cause, or simply don't care about who else might get hurt. Those people can't be deterred.

And threatening to kills lots of Muslims seems unlikely, somehow, to deter the North Koreans from selling nuclear weapons to terrorists.

The Koreans fall under the first category... any country that helps launch such an attack gets destroyed. I'm suggesting expanding, not narrowing, culpability.

Echo loudly the concerns voiced above. I just don't think we have any good moves in the bag. Retaliation threats are largely unnecessary. They're always implied. Regime change threats are, well, what they are... a mixed bag, a threat that can be safely laughed at under most circumstances. Today, I think it goes without saying that, if we were willing to lose our minds over 2 planes killing 3000 Americans, we're prepared to go even more disproportional if a nuke destroyed an entire American city. Thee question is, short of actually using the nukes, what can we really do, given both our limited resources and the large host of nations that view us with a jaded eye. Like it or not, the threat of growing American hegemony is viewed by most other nations as a concern that comparably daunting to that of islamic fundamentalist terrorism. That means that international cooperation is usually an uphill battle for us.

Deterrence is a form of persuasion, and thus it works only on the persuadable. I have a hard time believing there are more than a tiny handful of governments stupid enough to think that a successful nuke attack on the US would lead to good results for them or the planet that both we and they all live on.

But there are a BUNCH of governments who are convinced that things would go much better for them if they were able to acquire offensive nuclear capability for themselves.

IOW, everybody wants the biggest saber, but not for using, for rattling. Therein lies the conundrum. We're trying to prevent acquisition in order to guarantee against use. Our strongest backing there is our giant nuclear arsenal, I guess. But the big audience of nations eager to join the nuke club is likely to be able to stonewall and put us off on our goals of preventing acquisition. They all want in the nukes club, and they know both that our regime-changing tools are slow and limited,and our nuke arsenal is not morally useful except in retaliation.

The whole problem of nukes in a post-Cold War world (and probably even during the Cold War) is that they are essentially unusable. We aren't going to nuke an entire country because the government possibly financed a nuke attack against us.

As Bernie said, it would be difficult to prove conclusively and even if we did, what would we nuke? It would be nothing more than mass murder.

Regime change is easier said than done. Invading North Korea, for example, would be no piece of cake and the aftermath would probably be no different than in Iraq. And, as people have said, other countries pretty much know what are capabilities are. Making the threat explicit would simply limit our flexibility--which might be desirable in some ways (ie, making deterrence more credible)but could have very negative consequences.

The fact is, there aren't any good options. Obvioiusly, any country knows that we aren't simply going to sit back and do nothing after a nuclear attack. If they were going to sell nukes, they would try to cover their tracks completely.

I'm not against military action in principle but it seems to me that the only realistic way of deterring a nuke attack is to try to rid the world of fissile material and secure those sources that already exist. That means working with and, yes, talking to those countries that have or might have the capability of producing weapons or material to make weapons. I don't think there really is a viable military strategy that works in this case.

Nukes would be reserved for states like Russia and China that have nukes themselves, and the FBI is used for nuclear investigations, not intelligence agencies. BUT.

Justin points out, fatally for my idea:
But in any event, any country that would do so would accept those consequences beforehand.

...yeah. Just as Afghanistan did before and after 9/11. And Iraq did when they chose to invade a US ally. Oh, well.

I believe our deterrent should be that if a WMD attack is ever successfully committed against us, then we will cripple the Muslim world to greatest extent possible.

...but I'm afraid your idea won't work, either. Terrorists live for overreaction. I even speculate your idea was bin Laden's dream - after all, he was always fantasizing about Caliphates, and this is the only way that could happen. I'd say we DID overreact after 9/11, but if we'd held the entire Muslim world responsible, and, say, bombed every majority-Muslim capital, it's not atall improbable we would've created a global bloc of Muslims both at war with us and inclined to follow bin Laden's leadership.