Explainer | How Kim Jong-un kept expanding North Korea’s nuclear arsenal while appearing to seek peace with US

Of North Korea’s six atomic tests, Kim was responsible for four. Experts estimate North Korea has assembled 20-30 nuclear warheads

Trump says his diplomacy with Pyongyang prevented a war. But the North Korean missile testing and name-calling have since resumed

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US President Donald Trump with North Korean leader Kim Jong-un. Photo: AP

Published: 11:15am, 13 Dec 2019Updated: 11:31am, 13 Dec 2019

After an unprecedented series of meetings between US President Donald Trump and North Korean leader Kim Jong-un, negotiations over eliminating the latter’s nuclear arsenal have stalled. In the meantime, Kim has been busy making his nuclear arsenal bigger, deadlier and better able to strike South Korea, Japan, American forces stationed in Asia – and the US mainland.

Could Kim really hit the US?

He appears to be rapidly closing on that capability. North Korea could likely fit miniature warheads onto missiles and shoot them far enough – it successfully tested an intercontinental ballistic missile in 2017. It has also developed weapons that can be moved around more swiftly to evade detection. What’s less clear is whether Kim’s military could beat anti-missile systems and survive re-entry, or if they’re refined enough to strike their intended targets.

What about its bombs?

Of North Korea’s six atomic tests, Kim was responsible for four. They’ve come a long way since the first detonation in 2006 which measured less than 1 kiloton, leaving experts wondering whether it had been a partial failure.

The most recent, in September 2017, was the most powerful. Its estimated yield of 120-250 kilotons dwarfed the 15-20 kiloton US bombs that destroyed Hiroshima and Nagasaki in 1945. Experts estimate North Korea has assembled 20-30 nuclear warheads, the fewest among the nine nations with nuclear weapons.

A ground test of North Korea’s rocket engine, broadcast in Seoul. Photo: AP

How are North Korea’s weapons more nimble?

Kim has rolled out new solid-fuel ballistic missiles that are easier to move, hide and fire than many liquid-fuel versions. He has launched some two dozen since May including nuclear-capable, hypersonic KN-23 missiles that can strike all of South Korea – including US forces stationed south of Seoul – within two minutes. He has also launched KN-25 short-range missiles designed to be fired in rapid succession from a single launcher to overwhelm interceptors.

The new ballistic Pukguksong-3 missile – the biggest of the bunch – is designed to be fired from a submarine and has an estimated range of 1,900km. Weapons experts say North Korea also is developing an ICBM that uses solid-propellant technology, potentially giving the US less warning ahead of any strike aimed at the mainland.

Where does Kim’s military get its fissile material?

It has been self-sufficient for decades. The programme, which once turned out enough plutonium for one nuclear bomb a year, now relies largely on uranium enrichment and, according to weapons experts, produces enough fissile material for about six bombs a year.

The Trump administration says North Korea has enlarged its stockpile since nuclear talks began. Experts estimate the country has enough for roughly 30-60 nuclear weapons.