Clear factors differentiating an an offensive from a minimum deterrent nuclear capability

Question

Arms control specialist Cheryl Rofer argues that the nuclear weapon programs pursued by the dictatorships of Iran and North Korea were "Regime Change Deterrents":

The nuclear strategies of North Korea and Iran, up to now, are not the strategies of aggressors. They have left their options open to grow the programs in the future, but that is only prudent. The programs might be called “minimum deterrence.”

She bases this assessment on the fact that these countries produced or planned to produce a rather small number of weapons. A similar case might have been South Africa's nuclear weapon program, or maybe Pakistan up to a point.

My question is, can we define a cut-off point or area between a "minimum deterrent" nuclear weapons program and a more offensive one?

Candidates for cut off points might be: Numbers of weapons mated to delivery systems at any one time, numbers of warheads bigger than the minimum that allows economical maintenance (what would that number be? 5? 1? a dozen?) or a doctrine when to use these weapons. The biggest factor may be if there's a practical lower limit in size for a nuclear weapons program.

To use the Wikipedia definition of minimal deterrence:

Assuming that decision-makers make cost-benefit analyses when deciding to use force, China's doctrine calls for acquiring a nuclear arsenal only large enough to destroy an adversary’s "strategic points" in such a way that the expected costs of a first strike outweigh the anticipated benefits. [...] For example, the United States’ nuclear force exceeds the requirements of minimal deterrence, and is structured to strike numerous targets in multiple countries and to have the ability to conduct successful counterforce strikes with high confidence.

So we can conclude that somewhere between the nuclear arsenal sizes and structures of North Korea and the USA we have a phase change from minimal deterrence to soemthing else. Can we define a cutoff point, beyond which a nuclear weapon program is built for more than minimum deterrence?

Answer 1

The answer is a firm "it depends".

For example, it depends on your intended adversary, as well as technical capabilities. It also depends on your strategic goals (and what your foreign policy and military doctrine are).

1. Is your weapon capability - size and delivery combined - enough to inflict sufficient damage?

   If your notional adversary is China or Russia, 5 bombs don't seem much like an usable offense. You just tick the Chinese off, for no meaningful military edge.

   If your notional adversary is Israel or Singapour, just a couple of good bombs is enough to wipe most of the country off the map completely.

   North Korea probably falls under the latter bucket, since they can hit Seoul with just one warhead and be well ahead of the game.

2. Is your offensive strategy designed to start with the weapon, or to use the weapon as a backup/shield for conventional warfare?

   There's a difference between "defensive deterrent against attack to impose regime change" and "offensive deterrent against retaliation to conventional attack form you".

   As an example, look at Iran. They are clearly aiming to engage in various levels of armed conflict, typically via armed proxies (Yemen, Syria, etc...).

   To them, a South Africa style program (a small # of weapons) does not only serve as a regime change deterrent; but also, a deterrent against their opponents (e.g. Saudis, or Israelis in case of Iran) attacking them to counter such conventional warfare.

3. Another thing that Rofer's analysis misses is again proxies.

   Yes, to be a credible offensive weapon in a large scale war, more than a handful of warheads may be needed.

   But if your doctrine is to hand off your weaponry to a plausibly-deniable non-state actor (say, an unnamed one but it rhymes with Oh-la-la), this calculus changes dramatically.

4. To address a specific conern the OP raised in the comments re: is there some objective #:

   NO

   The reason is that, in order to arrive at a number that's "enough for deterrence, so anything above that is an overkill and therefore must be offensive", one must perform the nearly impossible (in practice) task: you (as a ruler of the country with nukes) need to accurately mentally model the mindset of your opponent county (or worse, countries) rulers, to accurately predict what would deter them.

   And in practice, you almost never can know that with any precision. Would 5 seem enough of a threat to those in opponent's government? Depends on their thinking, paranoya, assessment of yourself, doctrine, cocoroaches in the heads of individuals in that government, etc...

Answer 2

A minimum deterrent arsenal should provide a credible second strike capability. Just how many weapons one needs for that depends on their survivability, the presumed accuracy of the first strike, and the number of weapons it takes to inflict unacceptable damage on the adversary.

The first and second points are related, and they depend strongly on the assumptions of just what the adversary can do, and the third point depends on what he will accept.

For instance, I think it is a good guess that the US will not trade even one city for regime change in North Korea or Iran unless they view the war as inevitable and their attack as preventive/preemptive. So if a notional adversary had three weapons, each with a 50% chance of surviving the first strike and a 50% chance of an unintercepted flight, then this arsenal should give a 57% chance of one or more US cities being hit. A rational US president would not launch a first strike just for regime change.

If the notional adversary had 25 weapons, each with a 10% chance of surviving the first strike and a 10% chance of an unintercepted flight, there would be a 22% chance of one or more US city being hit. A rational US president would probably still shy away from the gamble, but that is much less certain.

The difference would be in the adversary's estimate of US precision strike and missile defense capabilities.

Against a regional opponent with no precision strike or missile defense, those 25 weapons would be plenty to use a few for offensive purposes and still keep a defensive reserve.

Answer 3

So in Nuclear Warfare, there are two types of targets: Counterforce and Countervalue. Counterforce is a target critical to a conventional or nuclear warfare, i.e. a group of ships, a military base, an airfield, nuclear silos, ect.

Countervalue are targets that are more civilian in nature, i.e. large cities and urban centers, whether or not there is military industry there. For example, targeting Washington D.C. is considered Countervalue because it is a major urban center... even though there is a lot of military leadership that can vital to military action.

Minimum deterrence is a counter value strategy which relies on Second Strike Only. You will likely not have enough nukes to consider a full second strike, but you have enough to put the fear of Countervalue retaliation into the target nation. The theory is to create a threat of a nuclear strike that would devastate enough of the nation that they would not want to initiate first strike. The problem is in dealing with each nation. The U.S.S.R. was quite concerned about losing Moscow because their government was quite centralized and almost every important U.S.S.R. leadership was in Moscow at any given time. The U.S. might be more accepting of a situation where ONLY D.C. was taken out because they're leadership is more distributed as is their manufacturing base.

With that in mind, the difference between defensive posturing with one Nuke and Zero Nukes is quite a lot. Japan was unwilling to surrender after Hiroshima because their thinking was that the United States couldn't make another nuke that fast. And then Nagasaki happened and Japan surrendered... of course, it was a very good thing that they weren't willing to risk a third city because at the time, we didn't have a third bomb. North Korea having a bomb does shake matters up a little and requires all parties to carefully consider what they are doing.

I would say that clear defining point of Nuclear War is when a nation achieves what is called "The Nuclear Triad" which refers to the three ways to deliver a nuke to a target: Ground Based Launches, Sea Based Launches (usually uses Submarines) and Sky based Launches (by both missile systems on a plane and gravity bombs). This ensures a greater level of threat to equal measure of nuclear force to an agressive attack. Like I pointed out in the comments, the United States assumed that if they were in a Second Strike scenario, they would lose 97% of their nuclear forces on First Strike. So they built their forces to assume the surviving 3% would destroy the U.S.S.R.

At preasent, four nations have the Triad: The United States, Russia, China, and India. France has historically had the Triad, but they removed ground based launch systems and now rely on air and sea only (ground based launches are best for First Strike). Additionally, everyone in the world knows Israel does have nuclear weapons, but it's also widely known that they have a nuclear triad... which requires nukes as part of that triad... or to be less cheeky, Israel being a nuclear power is officially denied by their government but it's widely known that they are a nuclear power and it's widely believed that they have the triad.

Answer 4

Number isn't a factor but range is. For example in North Korea, the max range of their nuclear arsenal, is very unlikely further than South Korea, which means, that they can't reach all the powers, which would, in a potential nuclear attack, would start nuclear strikes back against them.

That doesn't mean that any nuclear arsenal, that can reach every enemy is automatically offensive.

For example the Chinese and the Russians have huge nuclear arsenals but in both cases they are defensive. In case of China because they have far more powerful economical weapons and dependencies, that they can use. And Russia isn't aggressive against anyone.

But you can be relatively sure that a nuclear arsenal is pure defensive, if it isn't able to hit all potential enemy powers at once, unless the owner is an acting religious fanatic, in which case, every nuclear arsenal automatically becomes offensive. (And no Iran isn't that, even though US propaganda likes to tell people that)