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Category: Korea

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.

North Korean Nuclear Weapons as Economy of Force Pt 1: Effect & Cost of Long Range Artillery

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On June 19, 2018

In Korea, Military Theory

Recommended before reading this: If It’s Worth Doing, It’s Worth Doing with Made Up Numbers

North Korea last week offered to remove long range artillery from the DMZ.  But of course: they don’t need it anymore.  They’ve got nuclear weapons.  But what, exactly, is the logic behind replacing the conventional deterrent with a nuclear one?  After all, North Korea’s current deterrent system has worked.

North Korea’s long-range artillery (LRA) has up until now served as both a deterrent and as a deep-strike capability.  The North Koreans have no hope of conducting any meaningful air attacks against South Korean targets during a war, so they emplaced the LRA instead.  The artillery fire would be unobserved, but on the other hand most of the likely targets are static.

LRA represents a considerable investment in manpower and maintenance for the North Koreans.  Their main delivery systems, in order of increasing range and power, are the 170mm “Koksan” gun, the 240mm multiple rocket launcher (MLRS), and the 300mm MLRS.  The 170mm gun can reach the northern parts of Seoul, the 240mm rockets can reach most of Seoul, and the 300mm MLRS can reach down to Daejeon, threatening major installations south of Seoul.

I want to emphasize that this is a hypothetical to create an estimate for both the countervalue damage caused by this force, and give a rough estimate of North Korean investment.  Accurate numbers for the number of these systems in use are not publicly available, if at all.  Estimates are generally around “several hundred” 170mm guns, around two hundred 240mm MLRS, and fewer than a hundred 300mm MLRS.  We’ll assume that all artillery is organized into battalions of 12 pieces each.  We’ll go with 5x 300mm battalions (60 pieces), 15x 240mm battalions (180 pieces), and 40x 170mm battalions (480 pieces).

The Power of Long Range Artillery

Now we try to figure out how much damage these pieces can do.  The Koksan is similar to the American M107 175mm howitzer, which was used in Vietnam.  The M107 fires a ~150lb shell, at a rate of 2/minute, for 120/hr.  The shell is about 50% larger than a 100lb 155/152mm shell, so instead of a 50m casualty radius we will go with a 60m radius (inverse square law in effect).  To further specify, anyone within a 20m radius would be killed, anyone from 20-60m is wounded.  This is for an airburst against a person standing in the open however, not in a heavily built-up urban environment.  Relying mostly on intuition, I will quarter the casualty radius to make up for the natural cover provided by the surroundings and the tendency to seek immediate cover.

Assume the 240mm rocket is similar to the Russian 220mm Uragan, with a 220-lb warhead.  We’ll go with a 30m kill radius and an 70m wound radius in the open, down to 7.5/17.5 with the terrain adjustment.  Each launcher carries 22 rockets, which it can fire quickly, although it then needs to reload, reposition, and retarget.  Perhaps one salvo every 20 minutes, or 22×3 = 66 rounds per hour.

The 300mm rocket is probably similar to the BM-30 Smerch, with a ~500lb warhead.  40m kill radius, 80m wound radius (adjusted to 10/20m).  Each launcher has eight tubes, which it can fire in about a minute, although it takes a while to reload and reposition.  Again, one salvo every 20 minutes, or 8×3 = 24 rounds per hour.

This gives us 57,600 170mm rounds, 11,880 240mm rounds, and 1,440 300mm rounds per hour.  However, that’s an unrealistically high estimate.  Not all of the launchers work, not all of the munitions will explode…and not all of the warheads will contain high explosive.

The museum-piece Koksans might have a 50% readiness rate and a 20% dud rate.  They are now firing 28,800 170mm rounds, of which 23,000 will actually explode.  The newer, better-maintained MLRS might have a 70% readiness rate and a 10% dud rate, giving us about 7,500x 240mm  and 900x 300mm effective rockets per hour.

In an all-out scenario, some of those munitions will be fitted with chemical warheads.  I’ll look at the effects later, but if I had to guess then maybe 10-20% of warheads would be chemical.  Split the difference, call it 15%, and now we have 19,550x shells, 6,375x 220mm rockets, and 765x 300mm rockets exploding.

Since we’re considering this a countervalue strike, especially given the inaccuracy of these weapons, let’s look at Seoul.  Seoul has a very high population density of 17,000 people per square kilometer, or .017 people per square meter.  The 300mm rockets will probably be aimed past Seoul given their range, at relatively less dense targets like airfields and headquarters.  I will use the town of Osan, just south of Seoul, as an exemplar; it has 200,000 people in about a 43 square kilometer area, giving us .0046 people per square meter.

In the first hour:

Munition Eff. Rnds Kill Area (m2) Wound Area (m2) Pop/m2 KILL WOUND
170mm 19584 78.5 628 0.017 26,135 209,079
240mm 6361 176.6 785 0.017 16,979 75,464
300mm 771 314 942 0.0046 990 2,970

Total: 44,104 killed, 287,513 wounded

The ratio between wounded and killed looks a bit high to me.  Perhaps it includes relatively minor injuries that wouldn’t require immediate treatment.   A major hidden assumption, also, is uniform distribution of incoming shells: no round lands in the same place, and there isn’t even any overlap between casualty radii. Also, the firing batteries never run out of ammunition.

Once the first barrage lands, anyone in the target area will take cover.  I will model this as a further reduction in the casualty radii by 75%.  Also, counterattacks will begin; I will assume that these will reduce the attacking LRA by 1% per hour.  Summing the resulting series gets another 136,400 dead and 890,000 wounded before the LRA is silenced.

Assuming the 170mm shell is 15% high explosive filler (as is the usual 155mm shell), or 22.5lbs, the total amount of high explosive launched at Seoul is about 70 kilotons.  Keep that in mind!

Total: about 1.3 million casualties (180,500 dead, 1.1 million wounded wounded)

That’s just from high explosives, though.  What about the chemical weapons?

The largest chemical attack so far has been Halabja 1988 in Iraq.  At the time, Halabja looks to have had 70,000 people.  The attack, using a modern cocktail of lethal agents, targeted the city indiscriminately, killing around 3,500-5,000 and injuring about 7,000-10,000.  Halabja had and has a lower population density than Seoul overall, although it’s difficult to determine how much because most figures for the town clearly include sparsely populated surrounding areas.  Also, the high-rise residences common in Seoul would provide some protection against the heavier-than-air chemical agents.

Ignoring the confounding factors, a simple ratio means another 500k-700k dead and 1 million-1.4 million wounded.  Note that this would provoke the use of nuclear weapons by the United States in retaliation.  I am here using an assumption that the munitions discussed above produce a “blanket” that affects the target collectively, rather than trying to determine the effects of each given impact.  I believe this to be the correct approach based on my understanding of chemical warfare.  I’m not that confident in the reliability of this number, but I think it’s a good benchmark.

(It looks like the most lethal effect of the explosives might simply be to drive the population into shelters where they’re killed en masse by chemical agents sinking down.  People might be safer in their high rises; some accounts from the First World War noticed a similar dilemma, with chemicals lingering in trenches.)

The above gives us a total of about a million dead and two or three million wounded, many of whom would die later given the inability to treat so many people.  These three to four million casualties are probably an upper bound on what the North can achieve with its conventional deterrent.  For instance, it assumes no overlap between chemical and explosive casualties, which is silly, in addition to the absurd assumption of uniform distribution of munitions and generally zero overkill.  However, even this worst-case scenario wouldn’t actually annihilate Seoul, much less South Korea.  80% of the population in the target area would survive, and two-thirds would be relatively unscathed.

The Cost

We assumed above that the North Koreans maintains 60 battalions of artillery.  The American units with which I am most familiar have about 500 soldiers in a howitzer battalion and 250 in a rocket battalion.  However, these units are expected to operate with a great deal more independence and mobility than the North Korean units being discussed here.  If there are 200 soldiers in a North Korean LRA battalion, this gives us 12,000 soldiers. These are firing units, however; the total force is probably substantially larger, maybe 50,000.

Then there are the numbers of munitions.  The forces above fired over 1.4 million artillery shells, 420k 220mm rockets, and over 50k 300mm rockets.  Not a single one of these was fired in support of tactical maneuver.  Even assuming minimal costs of $300/shell, $1000/rocket, and $2000/rocket, this is around a billion dollars in munitions, against a GDP of under $30 billion, before even attempting to actually fight anybody.  The point is, it ain’t cheap.  This didn’t even attempt to include the expensive intermediate-range Scud-type missiles in the North, which are probably counterforce weapons, more or less.

Next, I’ll look at what why nuclear weapons might be an attractive replacement for all of this — which is what I originally intended to write about — in a follow-on post.

Edit: After I posted this, I found a much more detailed/competent/professional analysis of this problem by Mr. Roger Cavazos.  I’m encouraged that my first-volley estimate was at least in the ballpark of his more informed method.

What’s Possible with North Korea?

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On June 11, 2018

In Current Affairs, Korea

President Trump will meet with Kim Jong Un on Tuesday in Singapore. Nothing concrete will come out of this summit — the lack of South Korean representation guarantees that — but if things go well some sort of agreement is possible eventually.  Still, both sides have things to offer economically, diplomatically, and militarily.  What might that look like?

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