The rogue state conducted its sixth nuclear weapon test on September 3, but this was an entirely different prospect to the rest: a thermonuclear device carrying 150 kilotons worth of TNT, five times the size of the bomb that destroyed Nagasaki in World War Two.
Experts have agreed that it is now time to take Pyongyang’s threats seriously. The country’s illicit nuclear programme is continuing at a rate few predicted, despite the UN imposing ever stricter economic sanctions.
North Korea’s progress is all the more extraordinary when set against what we know about the secretive state.
This is a nation that suffers regular black outs due to energy shortages. Millions of citizens are facing a food shortage due to the worst drought to hit the country since 2001.
But yet the same state is now on the brink of developing a highly sophisticated nuclear weapon that only five world superpowers – the US, UK, France, Russia and China – legally possess.
So how did they do it?
Like much of everyday life in the hermit state, the precise details of North Korea’s scientific finesse remains a mystery. But there are some clues.
While some of the finer points of the nuclear fission techniques needed to build a hydrogen bomb are classified, a Pakistani physicist, AQ Khan, is alleged to have sold the secrets of the atom bomb to both Iran and North Korea in the early 2000s. North Korea conducted its first successful atom test in 2006.
Knowing how to build an atom bomb provides the essential blueprint for the dreaded H-bomb – but the speed with which North Korea appears to have attained this knowledge is still remarkable, and terrifying.
Just 11 years after that first atom bomb test, experts are talking about the genuine possibility that Kim Jong Un might soon possess a hydrogen bomb capable of being mounted onto a long range ballistic missile.
And it appears North Korea’s nuclear scientists have done it largely on their own.
Dr Martin Navias, from the Centre of Defence Studies at King’s College London, told The Telegraph: “The Chinese wouldn’t help them today, nor would the Russians, and neither Pakistan nor Iran have the necessary level of expertise.
“I would say they’ve done it independently, just moving forward a bit at a time.”
Tom Plant, director of Proliferation and Nuclear Policy at security think tank RUSI, told the same newspaper: “If a country puts its nuke programme at the top of the pile and has the will to weather the storms of sanctions and so on, then they can probably make it through.”
The fact is, under Kim Jong Un’s brutal regime, North Korea will be willing to let its citizens suffer to achieve its ultimate goal of becoming a legitimate threat to the world.