North Korea is one of the most isolated countries in the world.
The Korean peninsula was divided after World War Two and the North developed an authoritarian government.
Isolated globally, it saw nuclear weapons as its only deterrent against a world it believed was seeking to destroy it.
Could it carry out a nuclear attack?
Probably. North Korea has carried out six nuclear tests.
It claims, though this remains unverified, to have developed a nuclear bombsmall enough to go on a long-range missile.
It also has a ballistic missile experts believe could reach the US.
Why did nuclear talks with US materialise?
After months of escalating mutual threats, in January 2018 Mr Kim said he was “open to dialogue”.
Mr Trump accepted, ignoring the pre-talk conditions of past presidents ie that North Korea denuclearise first.
A new era?
In April 2018, the leaders of North and South Korea met. They agreed to find a way to end the Korean War and to “denuclearise the peninsula” – without agreeing what that meant.
Pyongyang ordered a halt to nuclear tests, freed US detainees and destroyed its nuclear research site.
On 12 June 2018, Mr Trump became the first sitting president to meet a North Korean leader.
The US and North Korea signed an agreement committing to the “complete denuclearisation of the Korean peninsula” but again didn’t say what that meant.
A new era – part II?
Since then, there has been little progress. The US wants North Korea to unilaterally give up its nuclear weapons while Pyongyang wants a step-by-step approach to ease the crippling sanctions regime.
In early 2019, Mr Trump announced a second summit for late February with both sides expressing hope for progress.