North Korea crisis in 300 words
The North Korean stand-off is a crisis that, at worst, threatens nuclear war, but it's complicated. Let's take a step back.
Why does North Korea want nuclear weapons?
The Korean peninsula was divided after World War Two and the communist North developed into a Stalinesque dictatorship.
Almost entirely isolated on the global stage, its leaders say nuclear capabilities are its only deterrent against an outside world seeking to destroy it.
How close are they?
North Korea claims it has successfully tested a hydrogen bomb - many times more powerful than an atomic bomb - that can be miniaturised and loaded on a long-range missile.
State media called the test "a perfect success", and although analysts said the claims should be treated with caution, leaked information suggests US intelligence officials do believe North Korea is capable of miniaturisation.
Pyongyang views the US as its main adversary but also has rockets aimed at South Korea and Japan, where thousands of US troops are based.
What has been done to stop them?
Attempts to negotiate aid-for-disarmament deals have repeatedly failed.
The UN has implemented increasingly tough sanctions - to little effect. China, the North's only real ally, has also put economic and diplomatic pressure on the North.
The US has now threatened military force.
Is it for real this time?
The crisis has been brewing for years, but is at a new level now.
The US is within reach of a strike now, which coupled with the miniaturisation is a game changer. And over the summer, North Korea has grown increasingly provocative, threatening the US Pacific territory of Guam and Japan.
The US responded to the latest test by saying its patience is "not unlimited" and it was ready to respond militarily.
Never has the rhetoric exchanged been more incendiary and personal, and experts are increasingly alarmed.