WASHINGTON (NYTIMES) - The decades-long war of words between the United States and North Korea escalated this week, when President Donald Trump on Tuesday (Aug 8) threatened North Korea with "fire and fury" if the rogue state continued its bellicose missile and nuclear tests.
Two days later, Mr Trump ratcheted up his rhetoric, saying it should be "very, very nervous" if North Korea even thinks about attacking the US or its allies, after Pyongyang said it was making plans to fire missiles over Japan to land near the US Pacific territory of Guam.
Keeping track of all of the weapons tests, sanctions and diplomatic talks can be dizzying.
Here's the background, along with some highlights of the long-running tension.
1. DOES NORTH KOREA HAVE NUCLEAR WEAPONS?
Yes. Intelligence reports suggest that the North Koreans have figured out how to miniaturise a weapon, but not how to deliver it intact to the US.
In 2016, Pyongyang released a photograph of its leader, Mr Kim Jong Un, posing with the country's first miniaturised nuclear warhead.
The New York Times (NYT) took a careful look at that image and concluded that the bomb - about 2 feet in diametre, with a destructive yield equivalent to the atomic bombs that the US dropped on Japan in World War II - could be carried by a long-range missile.
The North has steadily been building and testing such missiles.
On July 4, it launched a rocket that experts said was capable of reaching the mainland US. Officials say they believe the North already possesses medium-range missiles capable of delivering a nuclear warhead to much of South Korea and Japan.
On July 28, North Korea tested another missile that experts said was capable of hitting California.
But intercontinental missiles aimed at the US would fly in an arc into space before returning to Earth to hit their targets. The North is still working on a warhead that could survive the intense heat of re-entry as it plunges from space.
In addition to test missiles, North Korea has conducted five nuclear tests. Each test of its nuclear capabilities has been more powerful than the last, and it appears to be preparing a sixth test.
2. WHAT IS THE REACTION FROM NEIGHBOURING COUNTRIES?
The rising tensions have caused alarm among North Korea's neighbours, especially South Korea and Japan which would be most vulnerable to Pyongyang's aggression.
The North's rapidly advancing nuclear programme has prompted politicians in Japan and South Korea to push for the deployment of more powerful weapons, in what could lead to a regional arms race.
Some of the new capabilities under consideration in Tokyo and Seoul, Washington's closest Asian allies, are politically contentious. Adopting them would break with decades of precedent and could require delicate diplomatic finessing.
Markets were rattled, too, and stocks fell on Wednesday.
China, however, appeared to see an opening to present itself as the adult in the room and increase its regional influence.
3. WHAT IS THE REST OF THE WORLD DOING?
The United Nations Security Council has unanimously adopted a resolution to impose new sanctions on North Korea for defying a ban on testing missiles and nuclear bombs.
The resolution, imposing an eighth set of sanctions in 11 years, was intended to cut the country's annual export revenue by US$1 billion (S$1.4 billion), about a third of its current total.
However, a recent investigation by NYT reporters found that despite years of sanctions, North Korea still has ways - many of them illegal - to finance its weapons programme.
The paper also found that the North Korean economy is doing surprisingly well. Merchants and entrepreneurs, thriving under the protection of the ruling party, are encouraging a building boom in Pyongyang, and there are more cars in the capital than ever before.
On Monday, there appeared to be a rare opening to engage the North in diplomatic discussions. On the sidelines of a conference of South-east Asian foreign ministers in Manila, Philippines, North Korea's top diplomat held an uncommon round of talks with his counterparts from China, South Korea and Russia.
4. WHAT HAS TRUMP SAID ABOUT NORTH KOREA?
Days before his inauguration, Mr Trump said he would prevent North Korea from developing a weapon capable of reaching the US, tweeting, "It won't happen!"
In a television interview in April, he described Mr Kim as a "smart cookie".
Pyongyang has long used inflammatory language, previously threatening to destroy Seoul, South Korea, in a "sea of fire" and ordering North Korean missiles "stabbed into the throat" of US warships.
On Tuesday, Mr Trump invoked terms similar to those used by the North Koreans themselves, threatening to unleash "fire and fury" if Pyongyang endangered the US.
NYT's White House correspondent wrote that there was little precedent of a president using such language.
North Korea warned several hours later that it was considering a strike that would create "an enveloping fire" around the US territory of Guam.
Secretary of State Rex Tillerson said on Wednesday that Americans should not be concerned about an imminent threat: "I think Americans should sleep well at night, have no concerns about this particular rhetoric of the last few days." He said that as his plane stopped to refuel in Guam, the very island that North Korea had threatened.
5. WHO IS AT RISK OF ATTACK?
The US and its allies are unlikely to end the crisis purely by military means because pre-emptive action, no matter how surgical, could invite an aggressive response from Pyongyang, which has threatened to fire its missiles on Hawaii as well as on the mainland US.
In its latest warning, North Korea threatened to strike Guam, a US territory.
Guam, a Pacific island roughly the size of Chicago and home to about 160,000 people, is about 2,200 miles southeast of North Korea.
It is an essential base for the US military, which takes up about 30 per cent of the island. The military was considering increasing its presence on Guam by moving thousands of Marines there from Okinawa, Japan, according to the Associated Press.
In 2013, the US announced that it would speed up the deployment of an advanced missile defence system to the island as "a precautionary move" to protect its naval and air forces from the threat of a North Korean missile attack.
The system - Terminal High Altitude Area Defence, or Thaad - can be used to shoot down ballistic missiles, the type the North has been condemned for testing.
The North also has thousands of artillery pieces positioned along its border with the South and pointed at Seoul, a mere 35 miles from the border.
The arsenal is of limited range and could be destroyed in days, but US defence secretary Jim Mattis has said that if North Korea used those weapons, it "would be probably the worst kind of fighting in most people's lifetimes".
NYT recently took a detailed look at how North Korea might respond if the US tried a surgical strike and found that any attempt could set off a chain of events risking staggering numbers of casualties.
According to one analysis, 30,000 civilians would be killed in the initial bombardment - and that is without using nuclear weapons.
6. WHAT'S NEXT?
Mr Trump's senior officials are divided on how to proceed, and it is also not clear what Mr Kim will do.
The war of words between the US and North Korea so far has triggered much concern that the two countries will start a nuclear war, whether deliberately or inadvertently.
That said, there are five reasons why the threat is overstated, according to NYT's "Interpreter" columnists.
The five reasons are:
1. The US has been issuing vague threats against North Korea for more than 15 years, and North Korean leaders had correctly assessed the threats over the years as empty, never sending the countries careening into an unintended war.
2. Despite the war of words, action from the US, so far, signals calm and caution. American troops in Guam and Japan are still in their barracks. Naval warships are holding a respectful distance.
3. There is no incentive to escalate the situation, and both sides understand this. The US and North Korea's interests are to avoid a conflict. For Pyongyang, that is because it would lose in the event of war. For the US, conflict would risk a nuclear attack against an American city.
4. Countries tend to ignore unclear, isolated messages - such as Mr Trump's. His aggressive statements on North Korea appear to contradict his own administration's more measured lines. Studies on foreign policy messaging have shown that Pyongyang will likely hear Mr Trump's threats as empty.
5. For the US, empty threats would not damage its global credibility, according to extensive research and examples in history. Neither would they pressure the country to follow through on those threats.