HK GOT INT,L STRATEGIC CONSULTING LIMITED

SEOUL, South Korea — In China, the man threatening to fire missiles at the United States is often derided as a chubby brat. In the United States, a senator recently referred to him as “this crazy fat kid.” President Donald Trump once called him “a total nut job.”

But the target of all that scorn, Kim Jong Un, the 33-year-old leader of North Korea, has long been underestimated.

Kim was the youngest of three sons yet leapfrogged his brothers to succeed his father, Kim Jong Il. Many analysts dismissed him as an inexperienced figurehead when he took power at 27; some predicted he would never last. But almost six years later, there is little doubt he is firmly in control.

Now, against long odds, Kim is on the verge of making his isolated, impoverished nation one of very few in the world that can hit the United States with a nuclear-armed missile.

Some have urged Trump to open negotiations with him. But it is unclear whether Kim is interested in talking. He has made building a nuclear arsenal a top priority, arguing that it is the only way the North can guarantee its security and develop its economy.

His ultimate motives, like many details of his life, are uncertain. Since taking power, Kim has yet to travel abroad or host a visit from another state leader. Only a few people outside North Korea have been allowed to meet with him — the former basketball star Dennis Rodman, a Japanese sushi chef, the vice presidents of Cuba and China.

What little is known of Kim’s record suggests ruthlessness — and some ideological flexibility.

South Korean intelligence officials say Kim has executed scores of senior officials, including his own uncle, a wily power broker who had been seen as his mentor. He is also assumed to have ordered the assassination of his half brother, Kim Jong Nam, who was poisoned by VX nerve agent at the Kuala Lumpur International Airport in Malaysia in February.

Yet Kim Jong Un is also credited with loosening state controls on the economy and engineering modest growth, and regaining some of the public confidence that the dynastic regime enjoyed under his grandfather and lost under his father, whose rule is remembered for a devastating famine.

“Smart, pragmatic, decisive,” Andrei Lankov, a North Korea expert at Kookmin University in Seoul, said of Kim. “But also capricious, moody and ready to kill easily.”

Kim first appeared in North Korean state media in September 2010, little more than a year before he succeeded his father as supreme leader. Until then, it was not clear whether he would succeed his father. The outside world had never even seen a photograph of him as an adult.

The eldest son, Kim Jong Nam, was widely considered the heir apparent until 2001, when he was caught attempting to visit Tokyo Disneyland on a false passport. Kim Jong Il’s second son, Kim Jong Chol, was seen at an Eric Clapton concert in London in 2015, but it is unclear why he was passed over for succession. One of the only clues comes from Kenji Fujimoto, the Kim family’s former sushi chef, who wrote in a memoir published in 2003 after he escaped North Korea in 2001 that the elder Kim considered the child too “effeminate.”

But Kim Jong Il adored his third son, Kim Jong Un, and saw his own domineering attitude and other leadership qualities in the boy at an early age.

“He learned how power works from early age,” said Koh Yu-hwan, a professor of North Korean studies in Dongguk University in Seoul.

Kim is believed to have studied in public schools in Switzerland disguised as the son of a North Korean diplomat from 1996 until at least 2000. The classes were taught in German, and Kim struggled with the language. A video recorded at the time shows him uncomfortably tapping a tambourine in a music class.

There is evidence that Kim’s time as a youth in Europe, and perhaps elsewhere, left an impression. In his memoir, Fujimoto recalled conversations with Kim as a teenager in which the future leader expressed frustration with power shortages at home and marveled at overseas department stores. Kim suggested that North Korea should learn from China’s market-oriented economic policies, Fujimoto wrote.

Such accounts have left some analysts hopeful.

“When the time comes, Kim Jong Un is expected to adopt policies that will ease his country’s isolation and embrace good things from the West,” Paik Hak-soon, a North Korea expert at the Sejong Institute, a think tank outside Seoul, said in a paper on Kim’s leadership published in February.

But first came what South Korean officials have called a “reign of terror.”

After his father’s death, Kim’s hold on power is believed to have been precarious. Outside North Korea, many assumed he was the supreme leader in name only, with real power in the hands of Jang Song Thaek, his uncle and regent.

Jang appeared to help his nephew carry out a systematic purge, replacing many of the nation’s most powerful generals and bureaucrats, according to South Korean intelligence officials.

But two years into his rule, Kim moved against his uncle, too, arranging for him to be arrested by uniformed officers during a Politburo meeting while hundreds of party delegates watched. Jang was executed on charges that included clapping “halfheartedly” when Kim entered the room and plotting to overthrow him.

In total, since taking power, Kim is believed to have executed more than 140 senior officials.

“He moved quickly and ruthlessly,” said Daniel A. Pinkston, a Seoul-based expert in international relations at Troy University in Alabama. “I think most people did not expect a man so young to be so proficient at managing his dictatorship.”

Kim has improved access to food and goods by allowing more market activities. He has also launched a building boom in Pyongyang, where the most loyal citizens are allowed to live.

But conditions remain dismal outside the showcase capital, and further growth may require an end to the sanctions that limit the North’s ability to trade with the world. And that would mean giving up the nuclear program.

Kim, however, appears to see the problem differently. More than 30,000 North Koreans have fled since the famine of the 1990s, and defectors say he must keep the country isolated because he is afraid of it being swallowed by the South.

That is where the nuclear arsenal comes in. His government has argued that it needs nuclear arms to protect itself from being toppled like others who gave up weapons of mass destruction; the state news media has pointed to Moammar Gadhafi and Saddam Hussein.

But the North has also said it hopes to use nuclear arms to force the world, including the United States, to accept it as a full member of the international community on its terms.

“Kim Jong Un is here to rule for decades, playing the long game,” said Koh, the Dongguk University professor. “Over time, he believes that the world will have no option but to accept his country as a nuclear power.”