As North Korea moves closer to its first nuclear test in five years, one of the biggest worries for the U.S. and its allies might be a relatively small blast.
Kim Jong Un has made clear he wants to build an arsenal of “tactical” nuclear weapons, meaning lower-yield bombs that could be used on the battlefield rather than on whole cities. First it must produce miniaturized warheads to fit on the expanding array of short-ranged ballistic missiles it has designed to threaten U.S. troops and their allies in Asia.
This week, Kim said a barrage of missiles launched in recent days were intended for tactical nuclear strikes, while warning Washington that any attempted attack could be met by strikes at American forces in South Korea and Japan. The comments were a fresh sign that North Korea could be preparing for its first nuclear test since September 2017, something the U.S. has been ringing alarm bells about for months.
“To mass-produce tactical weapons, Kim Jong Un would need the seventh nuclear test with the purpose of making more powerful weapons, yet with lighter warheads,” said Moon Seong-Mook, a former general in South Korea’s military who is now the head of the Seoul-based Korea Research Institute for National Strategy.
While there were more than 2,000 tests of nuclear devices in the decades after the U.S. bombed Japan in 1945, North Korea remains the only country that has conducted physical detonations of atomic bombs this century, according to data from the Arms Control Association. Nuclear powers such as the U.S. now rely on supercomputers to simulate tests of their weapons to predict performance and reliability.
“I believe North Korea has succeeded in miniaturizing all warheads available, so they can be mounted on missiles,” Moon said.
Kim has embarked on a two-pronged nuclear strategy of developing tactical weapons for the Asian region and far more powerful thermonuclear devices for longer-range missiles that can hit the U.S. mainland. The U.S., Japan and South Korea have all said North Korea is ready to conduct a test at its mountainous Punggye-ri test site, where it has held all of its previous six tests.
“The DPRK clearly deems nuclear tests essential to be confident of its own nuclear weapons capability,” said Katsuhisa Furukawa, a senior analyst for the Open Nuclear Network, referring to North Korea by its formal name. “It would be reasonable to assume that the DPRK has considerably advanced its capability to develop miniaturized nuclear warheads.”
“Tactical” is an inexact term for a nuclear weapon that could be used within a theater of war, which to North Korea probably includes South Korea, Japan and U.S. assets in places such as Guam. A tactical weapon has a less powerful warhead and is delivered at a shorter range. The explosive yields can be of less than 1 kiloton, but many are in the tens of kilotons.
The atomic bomb the U.S. dropped on Hiroshima in 1945 had a yield of about 15 kilotons. North Korea’s last test of a nuclear weapon in 2017 had an estimated yield of about 120-250 kilotons.
Tactical nuclear weapons can still cause massive destruction and non-proliferation advocates argue their use could quickly spin out of control. Such concerns were evident in U.S. President Joe Biden’s warning last week that any use of such weapons by Russian President Vladimir Putin in Ukraine could lead to “Armageddon.”
Furukawa, who served on a United Nations panel of experts that monitored sanctions on North Korea, and other experts will be paying close attention whether the regime’s next test is at the site’s Tunnel No. 3. That is considered the likely place to detonate a low-yield warhead for a tactical weapon.
Tunnel No. 4, meanwhile, is believed to be reserved for testing a larger thermonuclear device, said Lee Choon-geun, a senior research fellow at South Korea’s Science and Technology Policy Institute.
Kim laid out a nuclear weapons plan just before Biden’s inauguration in January 2021 that called for smaller and lighter weapons. He also urged the development of a solid-fuel intercontinental ballistic missile that would be quick to deploy and strike strategic targets within 15,000 kilometers (9,320 miles) — a thinly veiled reference to the U.S.
He has fired his new short-range missiles from train carriages, a submarine and even claimed one in its recent barrage from late September was fired from a lake. That may help deter another confrontation with the U.S. like in 2017, when former President Donald Trump threatened “fire and fury” and officials talked of a “bloody nose” strike on the country as a preemptive warning.
Chang Young-keun, a missile expert at the Korea Aerospace University said there were additional difficulties when it came to building a warhead for an ICBM. Such missiles travel far above the planet and must withstand reentry forces at speeds greater than 3,200 kilometers (1,988 miles) per hour.
Kim has shown that he has mastered tactical delivery systems by testing almost 70 short-range missiles since 2019. These are quick to deploy, designed to evade U.S.-operated interceptors in the region and capable to hitting American military bases in South Korea in less than five minutes after launch.
“This means the short-range missiles are fatal to us,” Chang said.
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