For the first time in decades a US soldier is believed to be in North Korean custody. That is a scenario that could cause a diplomatic headache for the United States while it, alongside ally South Korea, tries to keep pressure on Pyongyang as the isolated nation ramps up its ballistic missile tests and bellicose rhetoric.

The US Army has identified the soldier who crossed the demarcation line into North Korea on Tuesday as Pvt. Travis King.

US military officials say King "willfully and without authorization" crossed into North Korea while taking a civilian tour of the Joint Security Area, a small collection of ​buildings inside the 150-mile-long demilitarized zone (DMZ) that has separated North and South Korea since the end of the Korean War in 1953.

"We believe he is currently in (Democratic People's Republic of Korea) custody and are working with our (Korean People's Army) counterparts to resolve this incident," US Forces Korea spokesperson Col. Isaac Taylor said in a statement.

Here's what we know so far.

Who is Travis King?

King is a cavalry scout who joined the military in January 2021. At the time of his rotation in South Korea, King was assigned to the 6th Squadron, 1st Cavalry Regiment, 1st Brigade Combat Team, 1st Armored Division out of Fort Bliss, Texas, according to Army spokesperson Bryce Dubee.

US officials did not say how long King had been in South Korea, but at some point he faced disciplinary action for assault and spent 50 days in a detention facility.

It is not known whether King spent that time in South Korean custody or in US military custody, but according to US officials, at some point after his release he was escorted to an airport for a flight back to the United States.

At the airport, King's escorts could not get past a security checkpoint with him, and at some point after that, he left the airport and later made his way to the tour of the Joint Security Area.

King is believed to be the first US soldier to cross into North Korea since 1982.

Why does this matter?

Relations between the United States and North Korea have been fraught for decades, but things are particularly difficult right now.

Tensions between Pyongyang and Washington have been rising, as the North has ramped up its nuclear and missile programs in the years following a breakdown in talks between former US President Donald Trump and North Korea's Kim Jong Un in 2019.

Those talks, which spanned three in-person meetings and saw Trump become the first sitting US President to step over the same demarcation line King crossed Tuesday, ended without any meaningful diplomatic breakthroughs.

To date, North Korea has tested intercontinental ballistic missiles three times this year and accused Washington and Seoul of inflaming tensions with military exercises and weapon deployments, including that of a US Navy nuclear-capable ballistic missile submarine to the South Korean port of Busan this week.

Last year, North Korea, test fired more than 90 cruise and ballistic missiles, including one that flew over Japan, in defiance of international sanctions. The uptick in testing has sparked concerns it may be preparing for a potential nuclear test -- its first since 2017.

The United States does not have official diplomatic relations with North Korea. Instead the Swedish Embassy in Pyongyang acts as a liaison for the US.

What are the risks for Travis King?

King is now in the hands of a notoriously autocratic and opaque one party regime that regards the United States as a mortal enemy.

What military intelligence value King could provide to North Korea is uncertain. As a private, he would not likely have access to top-level information, but just by being on a US military installation, he may be able to talk about things like base layouts or what units and numbers of troops are there.

But as a soldier and US citizen, King also gives Pyongyang a potentially powerful bargaining chip.

The United Nations Command, which oversees operations in the DMZ, said it was "working with our (North) Korean People's Army counterparts to resolve this incident." What North Korea might demand to return King back to US custody is unknown.

Or North Korea could use King for propaganda purposes.

A handful of US soldiers defected to the North Korean side in the decades after the end of the Korean War, but there has not been a recent defection.

And it is not clear at the moment what King's intentions were.

Even so there have been plenty of more recent instances where US nationals have come unstuck in North Korea or been held in custody, sometimes for long periods of time as US officials try to secure their release and Pyongyang looks to extract concessions.

What has happened in the past?

The last American known to be held by North Korea was Bruce Byron Lowrance, who, according to North Korean state-run media, crossed from China into North Korea.

Pyongyang accused Lowrance of working for the Central Intelligence Agency, but released him about a month after he was taken into custody, with the Swedish Embassy in North Korea facilitating the release.

The most famous recent case of an American being held in North Korea was that of Otto Warmbier, an American college student who went there as a tourist in 2016.

His planned five-day stay turned into a 17-month detention after he was accused of trying to steal a political banner from his hotel.

Warmbier was sentenced to 15 years hard labor on the charge, but was released to US officials in 2017. However, Warmbier's physical condition was poor, with Washington saying he had been tortured in custody.

He died less than a week after returning to the United States with severe brain damage.

Perhaps the most famous case of a US soldier crossing into North Korea was that of Charles Jenkins, a US Army sergeant who crossed into the North in 1965 while stationed at a US military unit near the DMZ.

Jenkins later claimed to have regretted his defection and blamed the decision on alcohol.

While in North Korea, he appeared in propaganda films, taught North Korean spies English and spent up to eight hours a day studying the writings of North Korean leaders.

He was allowed to leave North Korea in 2004, two years after his wife, a Japanese national who was kidnapped from her home in Japan in 1978, was allowed to leave North Korea under a deal between Pyongyang and Tokyo.