Not really. The worst sort of situation for a country to be in in terms of nuclear deterrence is to have only one nuclear weapon, because even though the threat of using it has significant power it would leave them utterly defenceless if they were to ever use one. It would be a weapon they could never realistically use, because they would be unable to deter the inevitably-devastating counter-attack, and so the threat itself would become baseless.

Having two or three isn't that much better, since it still leaves them with a finite supply and no way to replace the weapons once they reach the end of their usable lives. There's also always the possibility that a foreign power would be able to divine the locations of such a small number of bombs and be able to destroy or steal them all.

With its own program, a country can avoid all of those disadvantages by producing enough weapons to distribute them and maintaining strategic ambiguity about their exact number and location while possessing the capability to renew and replace the bombs as they age.

Terrorist groups, on the other hand, would be perfectly happy with just one nuclear bomb. Unlike a state, they don't have to worry about deterrence or their ability to carry out a second strike. But that's why the US and other countries have put a lot of effort into securing Russia's nuclear stockpile and part of the reason why there continues to be huge effort to prevent nuclear proliferation.

> There is got to be plenty of counties who would be prepared to pay a lot of money for such a device, since it guarantees that they will never be attacked by the US.

Not really. You need a device and a delivery mechanism. If either fail you are basically ending your country as an independent entity for the next couple of decades or so and you personally are unlikely to survive long after the failure.

If you have one device and declare it the general public will not believe it (some will, those "in the know" probably will if they can confirm it, but most will think it is tin-hat BS) so you need two devices: one to "test" openly and one to hold in reserve. If you bought a device rather than built it yourself the game enters a cat-and-mouse phase where a large fraction of US resources will be devoted to finding your device and blowing it up, if they succeed then you die shortly after.

If you get the device and just tell the US secretly that you have it then the cat-and-mouse game starts without the need for public posturing on either side and you (and most of the senior leadership of your country) are likely to find yourself on the unpleasant end of soft-power attempts at regime change and not-so-soft attempts that come from a busboy with a silencer.

There is a somewhat fuzzy critical mass of devices and reliable delivery mechanisms that are required before you are a threat with enough credibility to use your nukes as a shield. NK probably has a few nukes, but their artillery along the DMZ and the proximity of same to Soeul is really the only thing keeping Kim Jong Il alive; your hypothetical country has almost no hope of hitting the US and if it is not close to a US ally that its people actually care about then all bets are off. If Sudan suddenly declared that it had bought a nuke then you could probably measure Bashir's future lifespan in weeks...

so you're going to... nuke yourself? yikes.

Nope, you fall back so the nuke is behind the enemy's lines; classic ambush tactics. As an example, the Iraqis could have left a nuke buried behind themselves to knock out substantial US forces, if they had one. I haven't seen anything about it, but how much precautions the military took would tell you how seriously the gov't actually took their own claims about Iraqi nukes.

Another problem is that a nuclear weapon isn't just something you buy and keep in a lock-up until you need it, like, say, tanks or guns.

They need maintenance - the physics package decays (literally). For example, in fusion bombs, you have to replenish the tritium in the core, and in fission bombs you have to periodically replace the plutonium core.

There's a section about this in the Poundstone book "Prisoner's Dilemma: John von Neumann, Game Theory, and the Puzzle of the Bomb", and I don't recall the precise details, but this was a problem for arms control too. How do you count how many bombs a country has, when "bomb" is a loose term and bombs are kept in pieces, constantly being dismantled, replaced and upgraded.

If some guy claiming to be a Russian general offers to sell you what looks like a surplus nuclear warhead, how do you know he isn't a CIA or FSB agent running a sting? How do you know that he hasn't ripped out the electronics that control the timing of the implosion and sold them to someone else? How do you know that the guy who assembled that particular warhead back in 1973 was sober and followed all the instructions? (If you have eighty nuclear warheads in your arsenal, you have a credible nuclear deterrent even if each warhead has a 75% chance of being a dud. If you have one, not so much.)

>There is got to be plenty of counties who would be prepared to pay a lot of money for such a device, since it guarantees that they will never be attacked by the US.

Or it guarantees that if they are attacked by the US, it will be with a massive and overwhelming nuclear attack.

It also guarantees sanctions and other nice things.