Analysts paint a picture of potential catastrophe – chemical weapons launched across borders, an artillery bombardment on Seoul, nuclear strikes on major global cities and the most pressing real-world test for America's missile defence system.
When Barack Obama left office, he reportedly told incoming president Donald Trump the most urgent challenge he would face was that of North Korea.
North Korea has been working on developing its nuclear capabilities and intercontinental ballistic missiles (ICBMs).
It aims to develop the capability to mount a nuclear attack on the mainland United States.
The capability is necessary to defend the country from US aggression, the country says. It’s been pursuing the technology for more than 50 years.
North Korea claims it already has the ability to shrink a nuclear bomb onto a device small enough to fit on a missile – but it doesn’t yet have a functioning long-range projectile.
The US is determined to stop the rogue state from developing such capabilities, with the Trump administration ratcheting up diplomatic and military pressure on the country.
America is also continuing a cyber-campaign aimed at sabotaging North Korea’s capabilities, and has begun deploying a missile defence system in South Korea.
President Trump has said a potential war with North Korea could kill millions, and is counting on China to exert its influence over North Korea.
Should their efforts fail, the United States has refused to rule out a military strike on North Korea, with the Pyongyang administration also threatening potential pre-emptive strikes.
Military action from either side could trigger a potentially catastrophic conflict.
The decision to strike
The United States considers it relatively unlikely that North Korea would risk its survival by provoking the US with an attack on the country or its allies.
America’s nuclear weapons and sophisticated military function as a strong deterrent.
But heightened rhetoric on both sides has North Korean analysts worried.
Jenny Town, Managing Editor of 38 North and Assistant Director of the US-Korea Institute at the School of Advanced International Studies at Johns Hopkins University, says increased tensions means there’s an increased risk of errors being made.
“It’s basically a high-risk game of chicken being played between Trump and Kim Jong-Un,” Ms Town told SBS News.
“The higher the rhetoric gets, the higher the risk of miscalculations.”
USS Carl Vinson has been redirected to the region, with the aircraft carrier involved in a joint missile defence drill with the South Korean navy.
Malcolm Davis, Senior Analyst in Defence Strategy and Capability at the Australian Strategic Policy Institute, says that if North Korea keeps pursuing nuclear missile technology, it could push the United States into a first strike.
“The challenge is going to be in 18 months’ time, as North Korea gets very close to being able to put a nuclear warhead on an ICBM,” he told SBS News.
“The US would then be forced to act to prevent North Korea from being able to threaten the continental United States.”
Mr Davis says the development of a missile capable of delivering a nuclear bomb to the US mainland would be an intolerable red line for the superpower.
“We may not be able to stop it without fighting a major war on the peninsula, and we just have to get ready for that eventuality,” he said.
Ms Town is more wary.
“Having an ICBM is a big deal, but at the same time, our partners in the region would feel like the red lines are already crossed,” she said.
North Korea already has missiles capable of reaching South Korea and Japan, potentially with a nuclear warhead.
Ms Town is hopeful that diplomatic and economic pressure will bring North Korea to the negotiating table.
If development of an ICBM is a definitive red line which would trigger a major military response, President Trump needs to make that unambiguously clear in order to provide deterrence, Ms Town says.
It's advice President Trump doesn’t appear to be taking.
“I don't know. I mean, we'll see,” he said in a recent interview when asked if North Korea risked a military strike if it continued nuclear tests.
There’s no knowing exactly what a US first strike on North Korea would look like, but analysts speculate that it would have to be a major surprise attack in order to minimise the potential for retaliation.
While the locations of North Korea’s naval and air forces are relatively easy to target, the country also operates a fleet of hundreds of mobile short- and medium-range missile launchers, according to a 2015 Pentagon report.
The United States' Defence Department believes the on-road and off-road missile launchers - the type proudly shown in North Korean military parades - would be capable of targeting sites in South Korea and Japan.
“These are the kind of things that they put in place to ensure that people have to think twice before trying to engineer some kind of pre-emptive strike or regime change, as the North Koreans have seen in other countries,” Ms Town said.
Having witnessed the overthrow of regimes in Iraq and Libya, North Korea remains committed to its ballistic missile force as a form of deterrence, Ms Town said.
The missiles are within striking distance of major, global cities such as Tokyo and Seoul, as well as a number of US bases in the region.
The Pentagon has more than 73,000 personnel deployed in Japan and South Korea.
For its part, Australia has thousands of tourists in the region, and thousands more ex-pats who live there longer term.
While the US may have the technical capability to destroy the mobile missile launchers, pinning down their precise whereabouts at any one time is a challenge.
In reality, a number of short- and medium-range missile launchers would likely survive any initial attack, Mr Davis says.
“We may not be able to have the opportunity to take out those missiles before they’re launched, which means we then have to rely on missile defence to actually shoot down those missiles,” he said.
“And missile defence is not 100 per cent effective.”
Nevertheless, the US has begun installing a Terminal High-Altitude Area Defence (THAAD) missile defence system in South Korea, elements of which may be operational within days.
North Korean retaliation
Whatever the scale of an attack, analysts say the response from North Korea would likely be swift and unforgiving.
Ms Town says that any type of military strike would spark “a kinetic response, which could very easily escalate into war.”
“It would get really ugly,” she said.
In addition to missile capabilities, the United States also suspects North Korea of maintaining a chemical weapons program, with a stockpile of nerve, blister, blood, and choking agents.
The country also has a large, responsive, conventional land-based military - much of which is positioned to attack South Korea, and which the Pentagon believes could be activated with little or no warning.
The South Korean capital of Seoul – and its 25 million residents – are just 50km from the North Korean border.
“The carnage would be horrendous,” US Senator John McCain, Chairman of Senate Armed Services Committee, recently told CNN.
Mr Davis says any attack on North Korea is likely to draw “massive retaliation”.
“In some of the worst case scenarios we’re talking massive war on the peninsula. We’re talking North Korea unleashing massive artillery bombardments at Seoul, launching chemical biological, perhaps even nuclear weapons against South Korea and Japan,” he said.
“So we have to be prepared for that potentially.”
For years, China has provided a level of economic and military support for North Korea.
It has done so as a result of its own strategic calculations, says Professor Pei Minxin, an expert in US-China relations.
“For the rest of the world, the North Koreans appear to be irrational, crazy, aggressive. For China, North Korea is a very valuable piece of real estate,” he said.
“It provides a security buffer between the US and China.”
Without North Korea, America’s 28,000 troops in South Korea would be sitting right next door to China.
In 1950, the US and China were drawn into a devastating proxy war on the Korean peninsula.
But while China has been irked by the US maneuvering an aircraft carrier into the region and establishing a missile defence system on its doorstep, it's not certain the two superpowers would go to war over North Korea.
China’s support of its rogue neighbour has its limits, Mr Davis says.
“I think that they think that China is, to a degree, their security guarantor, but they probably recognise that China is not going to end up in a shooting war with the United States over North Korea,” he said.
“China would have the military option to intervene into North Korea, but the question is, would it do so? I suspect it won’t, I suspect it would keep its forces on its side of the border and just wait to see what happens.”
But war would have a significant impact on North Korea’s northern neighbour.
The fall of the regime would see streams of refugees flowing into China, analysts told SBS News.
“And in the ultimate worst-case scenario, if North Korea were to use nuclear weapons and the US was to respond with a nuclear strike, then you would get fallout drifting from North Korea into China,” Mr Davis said.
“So the Chinese don’t want war in the peninsula.”
While analysts may differ on the likelihood of conflict and the strategies to prevent it, there is universal agreement that in a war with North Korea, there is unlikely to be a ‘winner’.
The US risks tens of thousands of troops in the region, South Korea and Japan risk attacks on their major cities, the North Korean regime faces oblivion and China would have to deal with a humanitarian and strategic catastrophe just two hours’ flight from Beijing.
But while no country has an incentive for conflict, the strategic calculations of North Korea and the United States may prove irreconcilable.
“The real solution to this is for the US and China to somehow work together to remove this threat," Mr Davis said. "But the question is, how do you do this without risking major war on the peninsula?”
Much of the situation is uncertain because leaders on both sides of the stand-off are unpredictable.
“It is a chess game. I just don't want people to know what my thinking is,” President Trump said in a recent interview.
“Eventually, he will have a better delivery system. And if that happens, we can't allow it to happen.”
US Secretary of State Rex Tillerson has warned of “catastrophic consequences” if the world fails to stop North Korea's military development.
Ms Town says North Korean leader Kim Jong-un’s pursuit of nuclear deterrence is driven by rational strategic calculations, and hopes that negotiations can bring the situation back from the brink.
Mr Davis is not so convinced.
He says the young, inexperienced Supreme Leader cannot be counted on to think logically, with his escalating rhetoric driven by a desire to consolidate power internally.
“There’s nothing the outside world can do about that, that’s purely internal North Korean politics,” he said.
“There may not be a peaceful solution to this.”