Deterrence by threat of punishment, although a familiar concept that is comforting to many strategists, will therefore have utility if the government ultimately responsible for the bomb had acted knowingly and willfully. If North Korea sold fissile material or bombs to third parties, for example, it should be held accountable for the ultimate use of those ingredients of nuclear terrorism. The United States should make this clear to North Korea in advance.
Although deterrence through retaliation will play a limited role in most nuclear terrorism scenarios, the United States should have the capability to assure with a high degree of certainty and in a credible manner that it would eventually determine the source of the fissile material or nuclear weapons used against it. No government should believe it could attack the United States by using a terrorist group as a proxy and not be revealed and held accountable eventually. All governments should know that if they negligently permit theft or diversion of bombs or materials, they will be held accountable. Police and intelligence investigation could be powerfully augmented by radiochemical forensics, in which the debris from the detonation would be analyzed and compared to models of various U.S., Russian, Pakistani, and other nuclear-weapon compositions and designs.
Tracking down the exact source of the weapon, however, could take weeks of analysis under the best of circumstances and would be impossible unless others shared sensitive data about the design of all their weapons and the composition of all their supplies of fissile materials. Such data sharing is unlikely in advance of an attack, although it might suddenly become easier as these governments strive to show they are cooperating with an angry United States. Washington should seek to have the capability to attribute a nuclear detonation credibly and unambiguously to its source. It should state clearly as a matter of national policy that it will demand the cooperation of governments that might have been the source in proving or disproving their complicity. The United States should also state clearly that it reserves the right to retaliate against governments that knowingly transfer nuclear weapons or fissile materials to nongovernmental entities.
This isn't CSI: Waziristan. And talk of "eventually" holding those who would do this "responsible" can't mean a nice UN condemnation and a trial in abstenia in The Hague a decade later. Obviously, we must be careful about who we strike, but we must strike back with nuclear weapons.
Not every state that provides nuclear material to a terrorist group that hits us should be hit in retaliation. If the British are identified as the source of the nuclear material used in the terrorist bomb, I think we can safely assume that London was not plotting to hit us. If Iran complains that "rogue" elements of their government provided the material, I'm not convinced of their innocence.
So we must probably hit the supplier of the nuclear material--though not necessarily.
We must hit whoever hosted or supported the group with money or other resources.
We must hit whoever helped the terrorists get to America or an American target overseas.
And we must hit the terrorist group itself.
This does not mean we slaughter civilians like our enemies did. We hit the leadership or military forces associated with providing the nuclear material, aiding the terrorists group, or assisting the attack itself (or the military forces most threatening to us in the future), and any base area of the actual terrorists. We can supplement nuclear weapon(s) with conventional forces, but conventional forces alone cannot be the sole military response.
Further, we must do this quickly. Delay too many weeks and the world will get over the shock of seeing a mushroom cloud over Charleston and insist we show restraint. We will only have a narrow window to strike back and we must take it. Will it be weeks? Probably. Months? I don't know. Years later is definitely too late.
If we fail to strike back with the second nuclear weapon to be used in the Long War, nations and not just terrorists will learn to discount our nuclear forces if we can't rouse ourselves to act with the ruhtlessness that the situation requires. Our nuclear deterrence dies the very first time we are hit with an atomic device and fail to respond with a nuclear strike.
