By the rockets’ red glare

IN JANUARY North Korea detonated a nuclear device underground, its fourth such test and the first, it claimed, to show that it could build a thermonuclear weapon. In February it successfully launched a satellite. It has since been testing missile technology at a hectic pace. In March, its leader, Kim Jong Un, posed with a model of a nuclear weapon core and the re-entry vehicle of a long-range missile. On May 7th he told the congress of the Korean Workers’ Party in Pyongyang that his nuclear-weapons and missile programmes had brought the country “dignity and national power”. He boasts of his ability to “burn Manhattan down to ashes”.

The nuclear test, most experts believe, did not in fact demonstrate the ability to build a thermonuclear hydrogen bomb. The satellite does not seem to be working. Some of the missile tests failed. Mr Kim says a lot of nasty things. But there is a limit as to how much you can downplay this sequence of events. As Mark Fitzpatrick of the International Institute for Strategic Studies, a think-tank, puts it: “Just because Pyongyang wants us to pay attention, that doesn’t mean we shouldn’t.”

It is always tempting for America and other countries to put North Korea’s nuclear ambitions on the back burner of policy priorities, in large part because of a chronic absence of good options for dealing with them. But only an extreme optimist can today doubt that North Korea has developed missiles that threaten not just its southern neighbour but also Japan and, soon, the American base on Guam. Many experts, such as John Schilling, who writes about missile technology at 38 North, a website on North Korea run from Johns Hopkins University, believe that North Korea is on track to have a nuclear-capable missile with the range to reach the continental United States by early next decade—which is to say, within America’s next two presidential terms. Stopping that from happening needs to be a front-burner priority.

The history of unsuccessful responses to North Korea’s nuclear ambitions began in 1994, after Mr Kim’s father, Kim Jong Il, had threatened to pull out of the nuclear Non-Proliferation Treaty (NPT) (see timeline). The Clinton administration promised him two proliferation-resistant reactors—that is, reactors from which North Korea would not have been able to derive weapons-gradenuclear material—economic aid and an easing of sanctions if he agreed to freeze and then dismantle the country’s nuclear-weapons programme. This “Agreed framework” collapsed in 2002 when evidence of North Korean cheating became impossible to ignore. North Korea duly quit the NPT.

The next diplomatic efforts were the “Six-party talks”, which included China, Japan, Russia and South Korea as well as America and North Korea. They appeared to bear fruit in 2005 when America confirmed its recognition of North Korea as a sovereign state that it had no intention of invading, and North Korea agreed to return to the NPT, thus putting all its nuclear facilities under the oversight of the International Atomic Energy Agency (IAEA), and to forsake “all nuclear weapons and existing nuclear programmes”.

So different from Iran

Despite North Korea carrying out its first nuclear weapon test in 2006, the six-party-talks process somehow limped on until April 2009. Then, over a period of little more than seven weeks, North Korea tried to launch a satellite with a three-stage Unha-2 rocket in defiance of UN Security Council Resolution 1718, chucked IAEA inspectors out of its Yongbyon reactor complex and carried out a second underground nuclear test. Since then it has been pretty much downhill all the way. A final attempt at a deal based on aid in exchange for a testing moratorium in early 2012 was stillborn when North Korea announced a new missile launch only a fortnight later.

Faced with such a record of duplicity and intransigence, Barack Obama had apparently long since concluded that if he was to achieve anything in the sphere of nuclear non-proliferation, Iran offered at least a chance of success; with North Korea there was virtually none.

It was a cool calculation typical of the president. For a start, North Korea was a lot further down the road to a nuclear-weapons capability than Iran, which had remained within the NPT and was still a few years from being able to test a device. And Mr Obama realised there was also much more leverage to be had over Iran than North Korea. Bill Clinton had come close to authorising an air strike on Yongbyon in 1994, but pulled back in the belief it would trigger a new war on the peninsula that, by some estimates, could cost a million lives. After the nuclear test in 2006 the military option was off the table for good. That was never true of Iran. The Iranian leadership could not fully discount the threat of a pre-emptive strike by either Israel or America.

Sanctions were also a much more potent weapon against Iran than they ever could be with North Korea. Iran was vulnerable because it is dependent on oil and gas exports. And even though the country is only minimally democratic, its leadership has to pay attention to falling living standards and the anger they can bring. That helped make the removal of sanctions a greater priority than pressing ahead with the nuclear programme.

By contrast, sanctions have had a relatively low impact on North Korea’s closed economy. In large part that is because 90% of the trade it does is with China, which refuses to cut it off because of fears that a subsequent economic collapse would bring with it a torrent of refugees and the demise of a useful buffer against a close American ally. Nor does Mr Kim have to worry much about the political consequences of hardship for his people. So effective is the regime’s brutal system of control—anyone suspected of disloyalty may be killed or banished to a frozen gulag—that there was little sign of dissent even when hundreds of thousands died of starvation during the 1990s.

Lastly, Iran always (if implausibly) denied that it was seeking the capability to make nuclear weapons—the supreme leader Ali Khamenei even issued a fatwa that described possessing nuclear weapons as a “grave sin”. Mr Kim believes that nuclear weapons are essential. Like his father before him he has built them into the national narrative and iconography, seeing them as fundamental to the dynasty’s survival. Even without nuclear weapons, Iran is a regional power that America has to take seriously. North Korea has no other claim to fame except its nastiness. Its ruler sees nuclear weapons as the key to gaining the respect he demands from the outside world. They are not bargaining chips to be traded for other benefits.

You can observe a lot just by watching

That is why the evidence of an almost manic amount of nuclear-weapons-related testing since January is so alarming, and why interpreting what it means both in terms of political signalling and technical progress has become urgent. Gary Samore, Mr Obama’s arms-control adviser until 2013 and now research director at Harvard’s Belfer Centre, cautions how little outsiders really know for sure about North Korea’s capabilities. Jonathan Pollack, a Korea expert at the Brookings Institution, agrees the data are limited. Nevertheless, he says: “In the words of Yogi Berra, you can observe a lot by watching.”

David Albright, the president of the Institute for Science and International Security, a think-tank, and a former IAEA inspector in Iraq, has carried out detailed analysis of what is known of North Korea’s capacity to reprocess plutonium and enrich uranium. If the country is producing bombs similar in yield to the one that America dropped on Hiroshima—that is, of 10 to 20 kilotons, which would be small by modern standards, but would therefore require less-capable missiles for their delivery—his central projection is that it can produce enough fissile material for around seven warheads a year and that its current stockpile is about 20.

Mr Albright, like most analysts, is deeply sceptical that the device tested in January was, as Mr Kim claimed, a true hydrogen bomb. In hydrogen bombs a “primary”, which gets its power from nuclear fission in uranium or plutonium, sets off a “secondary”, which gets its power from the fusion of deuterium and tritium. Such bombs have yields in the hundreds of kilotons, or megatons. Estimates based on seismology suggest this year’s test, like its predecessors, had a yield of no more than ten kilotons, though the fact that the bomb was more deeply buried than the first three suggests its makers may have expected something bigger. Mr Albright suspects the engineers were trying a technique developed by South Africa’s defunct nuclear programme in which a lithium, deuterium and tritium tablet at the centre of a fission device boosts its yield with a bit of fusion.

The next issue is whether the North Koreans have graduated from devices that can be tested to devices that can be fitted onto either its existing medium-range Nodong missile (developed from the Soviet-era Scud C) or its two missiles under development, the Musudan intermediate-range ballistic missile (IRBM) and the KN-08 intercontinental ballistic missile (ICBM). Mr Schilling thinks that they would not have carried out four nuclear tests on something they did not think they could deliver. On March 9th, Mr Kim was photographed paying a visit to what may have been the Chamjin missile factory outside Pyongyang. In a hall packed with several ballistic missiles, Mr Kim posed beside a plausible-looking re-entry vehicle that would be consistent in size with a fission device about 60cm in diameter and weighing up to 300 kilograms. Both American and South Korean officials are convinced that North Korea can indeed make a warhead small enough to fit on the Nodong, which can reach targets in Japan, including American bases (see map).

A further question concerns the re-entry vehicle Mr Kim was proudly showing off: would it survive its passage through the Earth’s atmosphere? Until recently, Western intelligence believed that North Korea had not yet mastered this technology. But on March 15th pictures appeared in the North Korean media of what appeared to be a nose-cone from a KN-08 placed on an engine test stand one and a half metres beneath an ignited Scud rocket motor. Another picture (above, right) showed Mr Kim examining the re-entry vehicle after it had seemingly passed its test.

Another ground test on April 9th has, according to Mr Schilling, put to rest any doubts about North Korea’s ability to build an ICBM sooner rather than later. Two engines from Soviet-era R-27 submarine-launched ballistic missiles were coupled together to provide the propulsive power and range for a warhead carried by a KN-08 to hit the east coast of the United States. It is not known how many R-27s North Korea has, but up to 150 went missing from Russia in the post-Soviet 1990s. Mr Schilling reckons flight testing of a KN-08 enhanced in this way could begin soon, leading to a “limited operational capability by 2020”.

Other recent tests include a large solid-fuelled rocket motor of the kind needed to launch a mobile medium-range missile at very short notice (liquid-fuelled rockets, like those on the KN-08, take much longer to prepare for flight and are harder to move around) and the launch of a ballistic missile apparently from a submerged submarine in late April.

Not all North Korea’s tests meet with success. Three recent test fires of the Musudan flopped. Michael Elleman, a missile expert at the IISS, speculates that perhaps the missiles were solid-fuelled and the engines still at an early stage of development. Mr Elleman reckons that getting the Musudans working, and thus being able to threaten the American base in Guam over 3,000km away, must be a priority. He cautions that a string of failures is not grounds for optimism; the North Korean approach is to try it, find out what went wrong, find a fix and then validate it. “Their systems never work first time,” says Mr Schilling, “but they persevere.”

Some of what Mr Fitzpatrick describes as “this extraordinary amount of activity” may have been related to the seventh congress of the Workers’ Party, a sanctification of Mr Kim’s leadership. A less frenzied pace of testing may now resume. Since 2013, Mr Kim has talked of his byungjin policy of combining nuclear deterrence with economic development. Mr Pollack says that if Mr Kim wants the sort of bells-and-whistles deterrent deployed by the large nuclear powers, with submarine-launched and mobile missiles, the ruinous expense would make such a policy impossible. If, on the other hand, Mr Kim just wants what Mr Pollack calls a “don’t fuck with us” deterrent—one that keeps outside powers from interfering with his regime—he probably has one now.

Given what he has been testing, it seems likely that Mr Kim has his heart set on the former. His talk of economic reform—he laid out the first new five-year plan for decades at the congress—is short on specifics. If his enthusiasm for growth has led him to be worried by the supposedly tougher sanctions agreed to by the UN Security Council in Resolution 2270 on March 2nd in response to the nuclear test, he has shown no sign of it.

Deterrence, defence, despair

These latest sanctions reflect China’s increased willingness to co-operate with America and others on North Korea, a new mood born of frustration and annoyance that Mr Kim continues his nuclear provocations when China has asked him to stop. Still, unlike the sanctions on Iran, those on North Korea remain focused on hobbling the nuclear programme and denying luxury goods to Mr Kim and his cronies, rather than on damaging the general economy. North Korea is free to buy fuel oil and sell iron ore and coal as long as the revenues are not used to fund military activities. This is not a condition that can be practically enforced.

Chun Yung-woo, South Korea’s former chief negotiator at the six-party talks and national-security adviser to President Lee Myung-bak until 2013, says that although China has toughened its stance towards North Korea, it has “not fundamentally changed its policy of putting stability before denuclearisation—it will only implement sanctions that are tolerable to North Korea”. He hopes that the next American president, with support from Congress, will put China on the spot by applying a “secondary boycott” to any Chinese businesses trading with North Korea.

Another South Korean official, who talks regularly to the Chinese, is more sympathetic to their dilemma. The official says Beijing has been disturbed by an almost complete lack of communication with the North Korean regime since Mr Kim executed his uncle, Jang Song Taek, in 2013. Jang was the one senior figure in Pyongyang with whom the Chinese had close ties. The Chinese are changing their tactics, if not their strategy, in response to what they see as continuing provocations, looking for a sanctions “sweet-spot”—harsh enough to change Mr Kim’s mind but not so punitive as to risk the collapse of the regime. However, if Mr Kim believes he is now on the “home straight”, his instinct may be to sprint for the finishing line and talk afterwards. Mr Chun thinks that North Korea will never denuclearise; if it agreed to stop testing it would be because it had achieved the nuclear power and status it craves.

The rest of the world will not agree to that. Still, Mr Fitzpatrick says that some kind of high-level engagement is overdue: he thinks it preposterous that the only American who knows Mr Kim is Dennis Rodman, a retired basketball player. Peace-treaty talks with North Korea to bring about a formal end to the Korean war, he reckons, would not require recognition of North Korea’s nuclear status and could be part of an agreement to freeze nuclear-weapons development.

Mr Samore thinks Mr Kim’s behaviour may eventually exasperate China so much that it will bring into play sanctions which really hurt. In the absence of such leverage, though, the focus must be on strengthening deterrence and containment. That means resisting or defusing Chinese displeasure over the proposed fielding of the THAAD (terminal high-altitude area defence) ballistic-missile defence system in South Korea. The Chinese oppose THAAD on the basis that its powerful AN/TPY-2 radar could undermine the effectiveness of their nuclear deterrent against America, a claim that Mr Samore rejects.

China fears that, over time, a regional network of anti-missile systems deployed by America’s allies might come to threaten the deterrent effect of its relatively small strategic nuclear forces. In this instance that concern seems far-fetched. The THAAD system is designed to destroy missiles during the terminal phase of their trajectories, when they are coming back down; it can do nothing against missiles during their boost or midcourse phase, so Chinese missiles aimed at America would have nothing to fear from a THAAD battery in South Korea. Still, the Chinese claim to be worried that THAAD’s radars, if used in “look mode” rather than “terminal mode”, could reach deep into their territory.

Americans point out that using the radar that way would decouple it from the missile-defence system it was deployed with, which would defeat its purpose. More generally, they say that this is just something China will have to put up with. As America’s defence secretary, Ash Carter, said last month: “It’s a necessary thing. It’s between us and the South Koreans, it’s part of protecting our own forces on the Korean peninsula and protecting South Korea. It has nothing to do with the Chinese.” The message to China was clear: as you have done such a lousy job persuading your ally to rein in his nukes, you will have to accept the consequences.

Mr Elleman has calculated that, faced with 50-missile salvoes, a layered defence consisting of two THAAD batteries and South Korea’s existing Patriot systems would be able to stop all but 10% of what was fired. He and Michael Zagurek, in a paper for 38 North, base their calculations on what is known in the jargon as “single-shot probability of kill” (SSPK). With two layers of defence, the SSPK of each interceptor need only be a bit over 0.7 for 90% of the incoming missiles to be destroyed.

That would be an impressively effective defence against conventionally armed missiles. But only one or two nuclear warheads need to get through for the casualties to be immense (420,000 killed and injured in Seoul for each 20 kiloton warhead, reckon Mr Elleman and Mr Zagurek). And if nuclear-tipped missiles were launched alongside or behind conventional decoys the system would be clueless as to which was which. If Mr Kim were to add submarine-launched missiles to his arsenal, defence would be harder still; they could be fired out of sight of THAAD’s radar.

Like tougher sanctions, THAAD is well worth deploying. But neither can fully contain the threat. Nor is it certain that conventional deterrence (which rests upon the assumption that the regime to be deterred is sufficiently rational not to invite its own destruction) will necessarily work against North Korea. Another reason the Chinese give for their unwillingness to tighten the screw on the regime is that they fear its imminent collapse could result in a last act of suicidal nuclear defiance by Mr Kim. That may just be what Mr Kim wants his adversaries to believe. But if it is a bluff, it is not one that anybody wishes to call.