North Korea conducted two nuclear tests in 2016, one in January and another, its most powerful ever, in September. Add that to a string of missile tests, both land- and sea-launched, and the world has plenty of reason for worry.
"Combining nuclear warheads with ballistic missile technology in the hands of a volatile leader like Kim Jong Un is a recipe for disaster," Adm. Harry Harris, the head of the US military's Pacific Command, said in a December speech.
Bruce Bennett, senior defense analyst at the Rand Corporation think tank, went further still, saying Kim "might be considered the world's most dangerous man."
But just how much of a threat does North Korea pose?
Pyongyang's September test put North Korea's nuclear program in its strongest position ever, at least according to the Kim regime, which claimed to have successfully detonated a nuclear warhead that could be mounted on ballistic rockets.
North Korean state media said the test would enable North Korea to produce "a variety of smaller, lighter and diversified nuclear warheads of higher strike power." Western experts fear that could expand the range of North Korea's nuclear weapons, possibly putting Alaska, Hawaii or even the US mainland in danger.
The warhead tested in September was estimated to have a 10-kiloton explosive power, almost twice as large as the one tested in January, said Kim Nam-wook of South Korea's Meteorological Administration. The atomic bomb dropped by the US on Hiroshima in 1945 is estimated at 15 kilotons.
Despite Pyongyang's apparent progress on a warhead, Bennett, the Rand analyst, points out that North Korea's test of its delivery systems, those missiles and rockets, weren't promising enough to make it a global threat -- at least not yet.
"To be such, the North would need to have developed some form of reliable delivery mechanism for its nuclear weapons that could reach anywhere in the world. And the North has not yet done that," Bennett said, pointing out that of the eight tests of longer range missiles (2,000 miles or more), seven were considered failures, and the other was tested only over a short range.
And despite testing a submarine-launched missile in August, the North has only one submarine capable of launching such a missile -- and its range is short, making it unlikely to get past Western defenses to pose a threat beyond Asia, added Bennett.
Doubts about its delivery capabilities notwithstanding, North Korea remains the only country on Earth to test a nuclear weapon in the 21st century -- and that offers Kim considerable leverage, analysts say, especially with his continued ability to tolerate the West's only real weapon short of military action, economic sanctions.
"The sanctions would undoubtedly deter North Korea's economy and make the country further isolated ... but Kim Jong Un and his associates believe it is still worth it for them to have an advanced nuclear capability," said Seung-Kyun Ko, a professor at Hawaii Pacific University and a former research commissioner in South Korea's Ministry of Foreign Affairs.
Nuclear weapons are "a tool for giving the oppressed people pride and hope," Ko said.
The voraciousness of Kim's "nukes at all costs" philosophy was hammered home just this week when a high-ranking North Korean diplomat who defected to the South earlier this year said Kim wouldn't back down even if offered huge sums of money by Western powers.
Thae Yong-ho, formerly No. 2 at the North Korean Embassy in London, said Kim is "racing ahead with nuclear development after setting up a plan to develop nuclear weapons at all costs by the end of 2017."
The suggestion that Kim can't be bought off is echoed by Boris Toucas, a visiting fellow at the Center for Strategic and International Studies in Washington.
"Kim Jong Un has made the development of the nuclear program its main source of legitimacy, connecting his fate to what he sees as the greatness of his nation, well before economic progress," Toucas wrote in October, shortly after Pyongyang's second nuclear test of 2016.