Does North Korea have the H-bomb? Its most recent nuclear test is just the latest cause for alarm about this isolated Communist regime.

• Author: Smith, Patricia

North Korea is one of the most belligerent--and unpredictable-countries on Earth. So when its young dictator Kim Jong Un announced last month that his nation had exploded a hydrogen bomb for the first time, it was hardly a surprise. But it did alarm the entire world.

The explosion of a hydrogen bomb "could potentially shake up the security landscape of Northeast Asia and fundamentally change the nature f of the North Korean nuclear threat," said South Korean President Park Geun-Hye.

A hydrogen bomb is much more powerful than a conventional nuclear weapon, which North Korea has detonated three times before, and would represent a significantly increased risk--if North Korea's claims are true.

But there's wide skepticism about those claims. Officials in the U.S. and South Korea say the data from the impact of the explosion is not what you'd expect from a hydrogen bomb; it was more in keeping with that of a traditional atomic device.

But even if last month's nuclear test wasn't a hydrogen bomb, it was yet another reminder of the threat that a nuclear-armed, totalitarian regime like North Korea poses to America's ally South Korea and to the rest of the world. And it's further proof that North Korea continues to work on advancing its nuclear capabilities, despite international sanctions and ongoing pressure to abandon its program.

"This is North Korea thumbing its nose at the international community," says Richard Bush, a North Korea expert at the Brookings Institution, a think tank in Washington, D.C. "It reminds us that North Korea's ambition is to be a country with nuclear weapons."

For the U.S., North Korea's latest nuclear test is unwelcome news. It comes just months after the U.S. and five other nations brokered a deal with Iran to curtail its alleged nuclear weapons program.

Seven Decades of Conflict

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 (see "South Korea's Rise," above).

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 II, there was hope that he might modernize the country and 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 rule, North Koreans continue to live in a totalitarian "Big Brother" state, in which even thoughts are controlled--as George Orwell depicted in his novel 1984. Ordinary citizens have no Internet access, and TVs and radios receive only government channels. Homes are equipped with loudspeakers that blare state-sponsored slogans and sanitized news all day long and can't be shut off.

Food is scarce. When the Soviet Union collapsed in 1991, North Korea's economy, which had long relied on Soviet aid, began a catastrophic decline. While millions have starved, the regime has spent billions on a massive army and nuclear weapons program.

Anyone who dares to challenge the government is treated mercilessly. A 2014 United Nations report accused the Kim regime of committing "crimes against humanity" and estimated that there are up...