North Korea crisis in 300 words

Image from North Korean media of four missile launches on 7 March 2017 Image copyright Reuters

After a historic summit between the US and North Korea, here's an overview of a saga that has at times threatened nuclear war.

Why did North Korea develop nuclear weapons?

The Korean peninsula was divided after World War Two and the North developed into a Stalinesque authoritarian system.

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?

North Korea has carried out six nuclear tests. One, it says, was a hydrogen bomb.

It claims, though this remains unverified, to have developed a nuclear bomb small enough to be carried by long-range missile.

It also has a ballistic missile experts believe could reach the US, Pyongyang's main adversary.

In response the UN, the US and the EU have imposed tough sanctions.

Why did talks materialise?

Theoretically, North Korea was always open to negotiations.

But after months of sabre-rattling, it came as a surprise when Mr Kim said he was "open to dialogue" in January 2018.

Mr Trump then proved willing to ignore the pre-talk conditions past presidents have imposed.

When China backed sanctions, that further pressurised Pyongyang - though the North insists they weren't decisive.

A new era?

In April the Koreas' two leaders met and agreed to find a way to end the Korean War. They said they would "denuclearise the peninsula" - without agreeing what that meant.

Pyongyang ordered a halt to tests, freed US detainees and destroyed its nuclear research site.

Then on 12 June, Mr Trump became the first sitting president to meet a North Korean leader.

At their Singapore summit, Mr Kim reiterated his commitment to denuclearisation.

But observers said the document the pair signed did not explain the details.

Previous attempts to negotiate aid-for-disarmament deals have failed.

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