North Korea's missile and nuclear programme
North Korea is widely believed to have missiles capable of striking long-range targets, including potentially the US mainland.
It also claims to have developed a hydrogen bomb and to be able to mount it on a missile.
Despite the thaw with South Korea and the talks with the US, there is no indication Pyongyang has scaled down its military power.
Here's what you need to know about the North's missile and nuclear weapons programme and its military forces.Missiles that can reach the US
Throughout 2017, North Korea tested several missiles demonstrating the rapid advances of its military technology.
The Hwasong-12 was thought to be able to reach as far as 4,500km (2,800 miles), putting US military bases on the Pacific island of Guam well within striking distance.
Later, the Hwasong-14 demonstrated even greater potential with some studies suggesting it could travel as far as 10,000km if fired on a maximum trajectory.
This would have given Pyongyang its first truly intercontinental ballistic missile (ICBM), capable of reaching New York.
Eventually, the Hwasong-15 was tested, peaking at an estimated altitude of 4,500km - 10 times higher than the International Space Station.
If fired on a more conventional "flatter" trajectory, the missile could have a maximum range of some 13,000km, putting all of the continental US in range.
However, doubts remain as to whether these missiles could successfully carry and deliver a warhead for such a distance, and whether North Korea has the expertise to accurately hit a target.
In 2019, North Korea carried out a series of short-range missile tests, ramping up in July and August in what it called "warnings" to the US and South Korea over their military drills
Then in October, Pyongyang appeared to have developed a new capability when it test-fired a missile capable of being launched from a submarine.
In theory, being able to launch a nuclear-equipped missile from a submarine increases the range of North Korea's strike capability while also making its launch platform more difficult to detect. The threat is offset by the country's old and limited submarine fleet, which may be able to make a one-way trip to within range of Hawaii.
The apparent successes of all these tests has raised questions as to how North Korea's missile programme has improved so rapidly. Observers believe Pyongyang may have acquired high-performance liquid-propellant engines from illicit networks in Russia and Ukraine.
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On 3 September 2017 North Korea conducted by far its largest nuclear test to date, at its Punggye-ri test site.
Estimates of the device's explosive power, or yield, ranged from 100-370 kilotons. A yield of 100 kilotons would make the test six times more powerful than the bomb dropped on Hiroshima in 1945.
North Korea claimed this test was its first thermonuclear weapon - the most potent form of nuclear explosion where an atomic detonation is boosted by a secondary fusion process to produce a far bigger blast.
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American military intelligence believes that North Korea has successfully miniaturised a nuclear warhead to fit inside a missile.
In April 2018 North Korea announced it would suspend further nuclear tests because its capabilities had been "verified".
As part of the thaw in relations, North Korea promised to dismantle the Punggye-ri site and in May blew up some of the tunnels in the presence of foreign journalists but without any international experts present.
Pyongyang also told the US it would destroy all its nuclear material enrichment facilities - yet without a clear timetable most experts are hesitant to take the North at its word.Millions of soldiers
North Korea has one of the largest standing armies in the world - with more than one million soldiers and estimated reserves of some five million.
Much of its equipment is old and obsolete, but its conventional forces could still inflict massive damage on South Korea in the event of war.
North Korea also has around 200,000 special forces troops which could be expected to infiltrate the South in the event of any conflict.
They could potentially exploit a semi-secret network of 20-25 large tunnels which span the Demilitarized Zone (DMZ) - the border area - emerging behind South Korean and American forward lines.
A further threat comes from thousands of North Korean artillery pieces and rocket launchers deployed along the border. Their firepower could devastate South Korea, including the capital Seoul, which at a distance of less than 60km, is well within range.
Chemical weapons could also be used. In 2012 the South Korean government assessed that North Korea could have between 2,500 and 5,000 tons of chemical weapons, potentially one of the largest stockpiles on Earth.American forces in South Korea and the wider region
The United States has had a military presence on the Korean Peninsula since the Korean War. Today, South Korea has the third highest deployment of US troops anywhere in the world.
According to the International Institute for Strategic Studies (IISS) there are some 28,000 US troops stationed across South Korea including almost 9,000 air force personnel. In addition, the US has some 300 M1 Abrams tanks and armoured vehicles deployed.Image copyright Getty Images Image caption US strategic bombers have carried out training flights over the Korean peninsula.
Washington has also installed its controversial THAAD missile defence system at Seongju in South Korea, which would be used shoot down North Korean short and medium range missiles in the event of war.
In the wider region, Japan hosts more US forces than any other nation, with some 47,050 deployed, according to the IISS, the majority being naval personnel. It also has an aircraft carrier based in Japan.
There are also significant US forces on the US Pacific island of Guam, which is sometimes described as a "permanent aircraft carrier".
North Korea has previously threatened to fire missiles at the waters around Guam.