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Tag: Nuclear Weapons

Nuclear Deterrents Probably Don’t Work the Same for City-States

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On September 3, 2018

In Military Theory

Because decapitation strikes are too easy, or at least too dangerous.  A large country can mitigate this threat through dispersal of strike/retaliation capability, and by building early warning systems.  However, early warning only really works reliably when a strike can be detected a substantial amount of time (“a few minutes”) before it takes effect.

This is the logic behind bans on orbital weapons (de-orbiting weapons given less warning than ballistic weapons) and on the mutual withdrawal of nuclear weapons from Cuba and Turkey at the resolution of the Cuban Missile Crisis.  This is also the game theory logic behind countries like South Korea and Taiwan effectively outsourcing their nuclear deterrent to the United States. In The Dead Hand, David Hoffman quotes Zbigniew Brzezinski as saying that after detection, initial cross-checking, and message delay, the President has about seven minutes from launch to impact of a Russian (Soviet) ICBM to decide whether or not to order retaliation.  That window might have gotten slightly larger since the 1980s, but not by much.  The United States’ (and other existing powers’) nuclear strike capability is sufficiently dispersed not to be neutralized by local subterfuge, and highly likely to survive a a first strike.  This further reduced the likelihood of a launch on false-positive early warning.

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North Korean Nuclear Weapons as Economy of Force Pt 3: Conclusion

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On June 26, 2018

In Current Affairs, Korea, Military Theory

We took a look at the comparative effects of a conventional artillery attack and a nuclear attack on Seoul.  North Korea has maintained the ability to inflict tens if not hundreds of thousands of fatalities on the South using inaccurate and labor-intensive but voluminous long-range artillery fire for decades.  Nuclear weapons allow North Korea to maintain the threat of a countervalue attack on Seoul, while providing more flexibility than their current deterrent forces.  Also, the probable reliance of the North Koreans on chemical weapons in a shooting war means their legacy “conventional” deterrent already stands a high likelihood of provoking nuclear retaliation by South Korea’s American ally.

Even given high rates of missile interception, nuclear weapons allow the North Koreans to accomplish with a few munitions what previously took hundreds of thousands.  And antimissile defenses are not perfect.  Not every missile will be hit, and not every hit will actually kill the warhead.  The use of decoys and saturation salvos are likely tactics that would lower the intercept rate against North Korean missiles compared to those fired from Yemen in the linked article.

The nuclear deterrent is also more flexible.  Nuclear-tipped missiles can threaten not only all of South Korea — including important ports like Busan and Pohang that are out of reach of long-range artillery — but also off-peninsula support zones such as Japan, Okinawa, and Guam.  (North Korean nuclear ballistic missiles are probably useless against naval targets — they aren’t accurate enough and they can’t likely get target-quality data anyways).  They even open up the possibility of retaliation against the US mainland.

missile ranges

Ranges of North Korean missiles, 2016

Nuclear weapons can point not only to the south but to the north.  The North probably doesn’t consider China a threat in the same way they do the South Koreans or the United States, but there’s intents and then there’s capabilities, and China has a lot of capability sitting on the other side of a comparatively lightly-defended border.  If Kim thinks he’d ever like to do something the Chinese might not like — such as Korean reunification — he’ll probably feel a lot more comfortable being able to announce that any invasion would or could be met with nuclear retaliation.

The point is that the North’s nuclear weapons can replace their conventional deterrent while adding a lot of capabilities that howitzers and artillery rockets can’t, and it probably isn’t even costing them that much.  Again, North Korea can spend ~10% of its current defense budget on its nuclear program to replace an entire artillery corps, at the absolute minimum, and may set the stage both militarily and politically within the North for an even further drawdown of the North’s bloated conventional forces, a legacy of Kim Jong-Il’s “military first” economic policy.

North Korea isn’t the only country which has ever made this calculus.  The United States made a similar, deliberate choice in the 1950s to counter Soviet forces in Europe with nuclear weapons on the grounds of cost-effectiveness.  Stephen Schwartz of the Brookings Institution, who wrote the Atomic Audit book I cited in the last post, believes that this was ultimately false— however, he attributes this to the development of an excessive diversity of warheads and delivery systems, pork barrel politics, and mismanagement of the targeting process, NOT to the cost of nuclear weapons themselves.  North Korea, even if they are totally unaware of this history, is constrained by its poverty into not investing trillions of dollars into overkill.  One warhead type mounted on a few dozen missiles of various ranges — culminating in submarine-launched and intercontinental types — will suit them fine.

All of these benefits also suggest that North Korea’s nuclear weapons aren’t going away.  The “international community” has already “allowed” Pakistan, Israel, India, and the People’s Republic of China to build nuclear weapons.  The examples of Pakistan and Israel are particularly instructive: in both instances, a relatively small state threatened by larger neighbors (India, the Arab states) maintains a nuclear deterrent as an equalizer.  In many ways this asymmetric viewpoint is a more natural use of nuclear weapons than as one more asset in the arsenal of wealthy states with large militaries.

Robert Oppenheimer cropped

God created the nations, but J. Robert Oppenheimer made them equal.

North Korean Nuclear Weapons as Economy of Force Pt 2: Estimating Effects of Nuclear Weapons

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On June 22, 2018

In Current Affairs, Korea, Military Theory

In the last post, I looked at what sort of damage North Korea can do with its Long Range Artillery, including both conventional and chemical payloads.  Now we can try to estimate what the North can accomplish with nuclear weapons.  The number and type of nuclear warheads and delivery systems the North Koreans possess isn’t knowable, but using some publicly available information and making up plausible-sounding numbers can give us an idea of what they can accomplish.

Effects

North Korea has tested several some small Hiroshima-level ~15kt devices and, in their last test in 2017, a higher-yield ~100kt bomb.

Presumably the North Koreans are confident in their 15kt bomb design, which they claim will (unlike the bombs detonated in 1945) fit onto a missile.  There’s no reason not to believe them; if it doesn’t, they’ll just keep conducting tests until they have something that works and is small enough.  If they don’t set off another 100kt+ detonation, it’s an indicator that the 2017 test was of a missile-suitable warhead, which it probably was – -they don’t have much use for something that can’t be put on a missile.

I’m going to use Alex Wellerstein’s NUKEMAP app to estimate the effects of a nuclear explosion, and as a comparison to the uniform population density method from the last post.  He also has a “MISSILEMAP” app, but we’re not concerned with the ability to destroy a specific target; this is a countervalue attack against a densely populated area.

Playing around with the 15kt explosion on NUKEMAP, I get between 60-200k killed and 250-500k wounded depending on the nature of the district in which the bomb hits using Mr. Wellerstein’s model.  In the .017人/m^2 uniform density model from the last post, and the 1200m 500 rem dose radius as a kill radius (this area also includes a shockwave >5psi), we get 76,867 fatalities.  Using the 100% third-degree burns radius as the wound radius (1.9km) gives us 201,000 wounded.  So, this is in the ballpark of Wellerstein’s more detailed model, on the low end.  His model accounts for the possibility of casualties outside the radii noted above.  Mine is much more conservative.  I don’t put too much trust in the resolution of his population-density data, since the population shifts around the city substantially during the day and week.  Still, we’re generally in agreement.

nuke1

nuke2

Commercial/Government vs Residential

When discussing the damage done by conventional munitions, I decided to reduce the “damage radius” in order to account for the protection provided by the broken, built-up urban environment.  I don’t believe this to be the case with a nuclear detonation, because the large shockwave produced will tend to cause the total collapse of buildings, by applying the shockwave overpressure against a much larger area, compared to smaller conventional explosives.  This isn’t an inherent characteristic of nuclear weapons, and emulating this effect with non-nuclear explosives is the point of weapons like the GBU-43 or Timothy McVeigh’s hobby project.  However, none of the North Korean artillery warheads are anywhere near large enough to cause wholesale collapse of structures as in an earthquake.  It is possible that the construction of larger buildings in Seoul would enable them to avoid collapse collapse by one or several nuclear blasts.  If so, these are probably overestimates, but a lot of people are still going to die.

Aleppo_2014

Aleppo, Syria in 2014.  Despite heavy fighting, most of the buildings are basically intact.

Unfortunately, the paltry 15kt bomb is a firecracker compared to North Korea’s state of the art, for which I’ll use a conservative 100kt estimate.  Depending, again, on the district hit, NUKEMAP estimates 245,000-480,000 dead and 800,000-1,200,000 wounded.  Using our own model above — and 1600m/4500m kill/wound from the same source — gives us 140,000 dead and 1.1 million wounded.  This is almost certainly lowballing the number of people killed, since many outside the radius would be killed by building collapse, burns, radiation, etc.

nuke3

RIP Noise Basement

So, it looks like it would take 2-6x 100kt warheads or 5-15x 15kt warheads to inflict the same number of casualties as the conventional artillery barrage, while acknowledging that even one single warhead on target, especially the larger one, would do the job just fine.

Cost

We guessed in the last post that throwing 70 kilotons of high explosives at Seoul would cost about a billion dollars worth of munitions and require 50,000 people.  The North Koreans’ job isn’t quite so simple as it appears above, because not every warhead can hit its target.  If South Korean missile defenses can intercept 75% of incoming missiles, then the North need to launch 8 missiles to get a 90% chance of hitting.  Even 50% interception rate means you need 3-4 missiles for a 90% probability of hit.  Better, but do you feel lucky?

So, the North wants some combination of suppression and saturation of missile defenses in order to actually hit the target.  If launching missiles in salvos reduces interception rates to 50%, and suppression of missile-defense sites (such as by maintaining a small fraction of the conventional artillery above, or by using small drones as improvised precision munitions) can get the interception rate to  33%, now we’re in business.  Launch a five-missile salvo, 99% chance one goes off.

Nuclear disarmament advocate group Global Zero estimates that North Korea spends about $700 million per year on its nuclear program, compared to about $10 billion on its military overall.  Estimating the marginal cost of a nuclear weapon is very difficult even in the best of circumstances. The 1998 book Atomic Audit estimates that China spent $28 billion in 1988 dollars ($58 billion in 2017) to build 450 nuclear warheads, about $120 million apiece.  The comparison is apt given the similarities of a relatively poor state with modest aims.  This article estimates a marginal cost of $50 million for an American ICBM.  Given their possession of a workable warhead design and nuclear material, it is far from unreasonable to assume that North Korea can build and maintain 10x 100kt IRBMs and a flock of decoys for less than the billion dollar stock cost of its conventional deterrent munitions.

This also means that if nuclear forces allow the North Koreans to decrease spending on conventional forces by 10%, they’re coming out ahead.  Spinning this shift as “conventional disarmament” even allows them to parlay the weapons program that in theory contributes to their pariah status into a diplomatic positive.

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