A version of this story will appear in Upfront's September 18 issue.

For the U.S., the latest escalation is particularly unwelcome news. President Trump took office in January promising to get tough with North Korea and finally deal with the threat it represents—a goal that eluded three previous presidents. Over the past two decades, the U.S. has alternately tried negotiating with North Korea and punishing it with tough economic sanctions. Neither approach has worked.

In August, the United Nations Security Council unanimously passed a new round of sanctions against North Korea that are expected to cut the amount of money it earns from exports by $1 billion—a third of its total. In response, North Korea ramped up its threats, declaring, “There is no bigger mistake than the United States believing that its land is safe across the ocean.”

North Korea has a long history of antagonizing the international community, and the U.S. and North Korea have been at odds for seven decades. The roots of the conflict go back to the end of World War II.

In 1945, the Soviet Union occupied Korea north of the 38th parallel and installed a Communist regime, while U.S. and Allied forces controlled what became South Korea. The North later invaded the South, and the Korean War (1950-53) followed. That conflict, in which 34,000 Americans died, ended in a stalemate, leading to two very different nations.

South Korea developed into a thriving democracy with a strong, high-tech economy. It’s long been a staunch American ally, with 28,000 U.S. troops stationed there to protect South Korea. 

North Korea, on the other hand, became a Communist country and one of the most repressive and isolated regimes in the world. When Kim Jong Un, then in his late 20s, inherited the dictatorship after the 2011 death of his father, Kim Jong Il, some hoped that he might improve relations with the international community.

But he’s proved to be as ruthless as his father and his grandfather, who founded the regime. He’s continued to test missiles and even threatened a nuclear strike against South Korea and the United States. In 2013, Kim ordered the execution of his uncle—his second-in-command and mentor—for allegedly plotting a coup. There were also unconfirmed reports that Kim had his uncle’s entire family, including children, executed as well. 

Under Kim’s brutal rule, most North Koreans continue to live in a totalitarian “Big Brother” state like the one George Orwell depicted in his novel 1984. Ordinary citizens have no internet access, and the government tries to keep all information about the outside world from reaching its citizens. From a young age, North Koreans learn that the U.S. is their greatest enemy.

“I grew up believing that Americans were not human, that they had horns and tails—because that’s what my teachers told me,” says Sungju Lee, who escaped from North Korea when he was 16. “The government’s main concern is protecting their regime.”

Anyone who dares to challenge the government is treated mercilessly. Smugglers sell Hollywood movies and South Korean TV shows on thumb drives or DVDs, but anyone caught watching them by the secret police risks arrest.

A 2014 United Nations report accused the Kim regime of committing “crimes against humanity” and estimated that there are as many as 120,000 political prisoners in four camps. Starvation, the report says, has been used to control and punish North Koreans, both in the camps and in the general population.

While much of North Korea remains deeply impoverished, its economy has begun to show some signs of life since the younger Kim took power. Dozens of marketplaces have opened in cities across the country, a small class of politically connected merchants and entrepreneurs is developing, and the capital, Pyongyang, has seen a construction boom. This improving economic picture—at least in cities and elite circles—has made it easier for the government to withstand the pressure of international sanctions and still finance its nuclear program.

But in much of the countryside, food remains scarce. And while millions have starved—especially in the 1990s during particularly severe famines—the regime has spent billions on a massive army and nuclear weapons program.

With so many problems at home, Kim seems to have calculated that cementing the country’s status as a nuclear power will boost his standing and distract North Koreans from their plight. Kim says that the threat of sanctions or military action against the North “only strengthens our resolve and further justifies our possession of nuclear weapons.”

Trump, like many presidents before him, has been frustrated with China’s failure to rein in North Korea. China is North Korea’s main ally and biggest trading partner, and China has historically called its relationship with North Korea “as close as lips and teeth.” Trump recently tweeted that the Chinese “do NOTHING for us with North Korea, just talk.”

But in August, China did vote in favor of the new U.N. sanctions. It remains to be seen, however, whether China, which fears chaos on its border if the Kim regime collapses, will actually enforce the new economic restrictions.

Secretary of State Rex Tillerson has said that “all options are on the table” for dealing with North Korea. Those options include negotiations or more economic sanctions—neither of which have worked so far—and the implied threat of a military strike against North Korea. Experts say using military force is extremely risky and could prompt the resumption of an all-out war on the Korean Peninsula with millions of casualties.

The reality, most experts say, is that there isn’t really a good solution: Fundamentally, the U.S. lacks much leverage to convince the North Koreans to change course, and the Chinese have their own reasons for not wanting to apply too much pressure. 

“The fact is they can build missiles faster than we can impose sanctions, so they’re winning the race,” says Jim Walsh, a North Korea expert at the Massachusetts Institute of Technology.

Bush, of the Brookings Institution, agrees that finding a way to make North Korea give up its nuclear weapons program isn’t likely.

“If there was a solution to this,” he says, “we would have had it a long time ago.”

With reporting by Peter Baker and Choe Sang-Hun of The New York Times.