In recent weeks, the North Korean government has ratcheted up its rhetoric to ever loftier heights, even threatening to rain nuclear fire on the United States. That understandably has fueled concerns, but what can the North Korean military reliably do?
On April 11, a member of Congress cited a Defense Intelligence Agency report stating that DIA had “moderate confidence” that North Korea had mastered the ability to put a nuclear warhead on top of a ballistic missile. That triggered new concerns, followed by a rush of qualifications. Director of National Intelligence James Clapper released a statement saying “North Korea has not yet demonstrated the full range of capabilities necessary for a nuclear-armed missile.” A spokesperson for South Korea’s Ministry of Defense expressed “doubt that North Korea has reached the stage of miniaturization.”
So what’s going on?
In order to have a nuclear-armed ballistic missile, North Korea must master three challenges: it needs a nuclear weapon; it needs to miniaturize the weapon so that it can fit inside a ballistic missile warhead and withstand the stresses of flight; and it needs a ballistic missile to deliver the warhead. To provide a credible military capability, it must be able to do these things reliably.
As to the first question, North Korea has nuclear devices. It has conducted three underground explosions, although many judged the first two—conducted in 2006 and 2009—to be partial failures, particularly given their low yields. The 2013 test appears to have been more successful.
Jeffrey Lewis at the James Martin Center for Nonproliferation Studies notes that North Korea could take one of two approaches to developing a nuclear bomb. One route, which most other nuclear weapons states followed, is to first test a “simple fission device.” That’s big and heavy—no North Korean missile could carry it—and it produces a yield of 15-20 kilotons, much larger than any of the three North Korean tests. Lewis thus inclines to think the North Koreans are developing a miniaturized weapon, which would produce a smaller yield.
This gets to the second question: the need to fit a nuclear weapon inside a ballistic missile warhead that can withstand the stresses of launch, flight and reentry. North Korea may be working on miniaturizing a bomb to fit in a missile warhead. We do not know how successful, or unsuccessful, they have been. We do not know the size of the three devices they tested.
We do know that the North Koreans have not successfully flight-tested a ballistic missile warhead to a range greater than 1300 kilometers. They have tested and deploy Hwasong and Nodong missiles with ranges up to 1300 kilometers, but longer range missiles mean greater stresses on the warhead. For example, an intercontinental ballistic missile (ICBM) warhead reenters the atmosphere at a speed of five-seven kilometers per second or 10,000-15,000 miles per hour. Higher velocity means more heat and requires more weight to protect the “physics package” of the warhead, which has to survive and function in a very stressful environment.
The third question has to do with ballistic missiles. North Korea is estimated to have 550-600 Hwasong-5 and -6 missiles, variants of the venerable Soviet SCUD, which was first flown in the 1950s and exported around the world. The Hwasong missiles have ranges of 300-500 kilometers, giving them the capability to target South Korea. North Korea’s Nodong missile is an enhanced SCUD. Some 200 are estimated to be deployed. With a range of 1000 to 1300 kilometers, they could reach targets in Japan in addition to South Korea.
For ranges beyond the Nodong, there are much more serious questions about the reliability of North Korean ballistic missiles. The Musudan intermediate-range ballistic missile—two of which reportedly now sit on mobile launchers near North Korea’s east coast—is estimated to have a range of 3200 kilometers. However, the Musudan has never been flight-tested. As Greg Thielmann, a ballistic missile expert with the Arms Control Association notes, a missile that has not flown cannot seriously be called operational.
The Taepodong-1, with a range of 2200 kilometers, has flown once, in 1998 as a space-launch vehicle. Its third stage failed. Over the past seven years, the ICBM-class Taepodong-2 is one for five in flights, none of which demonstrated a warhead reentry capability. The one success, last December, was a space-launch variant called the Unha. All three stages worked, though the satellite apparently was left tumbling uselessly in orbit. Finally, there is the KN-08, reputedly an ICBM-class missile, which paraded through the streets of Pyongyang last year. Several theories address it, including that it is a developmental missile or just a fake. It has never flown.
This test history raises serious doubts about North Korea’s long-range missile capabilities. As a 2012 RAND report by Markus Schiller notes, the United States tested its Atlas ICBM 125 times before it became operational, while the Soviet Union tested the R-16 ICBM 90 times before making it operational. In the 1980s, when the United States had much more experience with ballistic missiles, it still conducted 30 developmental flights of the Trident II submarine-launched ballistic missile.
This is rocket science. Are North Korean engineers so good that they can glean from a handful of flight-tests—or no tests—the information needed to produce a reliable missile, when others conducted dozens of flights? The North Koreans undoubtedly are learning more about missiles (and about reentry vehicles and nuclear weapons), which is of concern. But as General Clapper said, they have not demonstrated the full range of capabilities.
The North Korean leadership bases a big part of its foreign policy on bluster. As an element of this, declaring unproven missiles to be operational makes sense. In such a strategy, it may be less important that the ballistic missiles work reliably—or at all—if one can bluff the outside world into fearing that they do.
[On President Moon Jae-in's definition of a 'red line' for North Korea] The only way we will know definitively that North Korea actually has a nuclear-armed missile that works is to demonstrate this capability...It would be considered an act of war which others would see as justifying preemption, and retaliation if preemption or missile defense did not work.