When Kim Jong Un first appeared in Pyongyang’s carefully stage-managed public spotlight in the fall of 2010, North Korea watchers began scouring for clues to learn whether the pudgy heir apparent would be a reformist or simply the newest face of a despotic regime.

Nearly 16 months after taking the reins of the hermit state following the death of his stoic father, North Korea’s 30-year-old leader appears to be careening toward the latter — at least on the surface.

Having disavowed his country’s armistice with South Korea and threatened to fire his increasingly capable missiles toward the United States, Kim has put the Korean Peninsula and Washington on a war footing. His behavior follows the playbook of his predecessors, with one notable and potentially dangerous departure that appears to have him backed into a corner.

“His father and his grandfather always figured into their provocation cycle an off-ramp of how to get out of it,” Adm. Samuel Locklear III, the commander of U.S. troops in the Pacific, told Congress this past week. “It’s not clear to me that he has thought through how to get out of it. This is what makes this scenario, I think, particularly challenging.”

Making sense of the Kims has been more of an art than a science. A cadre of North Korea scholars has spent decades piecing together a portrait of the eccentric, secretive family by poring through mounds of propaganda, defector accounts and the limited, sporadic contact the regime has had with the West. While acknowledging that Kim Jong Un remains an enigma, experts in the intricacies of Pyongyang say a careful study suggests his recent bout of bellicose rhetoric probably represents a desperate cry for legitimacy rather than a genuine appetite for combat.

By declaring war on South Korea, he seems to be channeling his firebrand grandfather, Kim Il Sung, the iconic founder of North Korea who plunged the region into a war that killed as many as 5 million people, including 35,500 American troops, in the 1950s. U.S. officials are on alert for a new provocative act tied to the elder Kim’s birthday, which is widely celebrated in North Korea, on Monday.

As Kim Jong Un eases into the top job of a nation whose elite has long been presumed to be rife with intrigue and rivalries, he appears determined to assert a tight grip on the levers of power.

“He has an inferiority complex,” said Kongdan Oh Hassig, a North Korea expert at the Institute for Defense Analyses in Alexandria. “He is trying to show that he has a strategic mind, that the military stands behind him and that no one stands against him.”

There are major gaps in the public biography of the new leader, the third son of Kim Jong Il. But as he has assumed an increasingly public role, Kim Jong Un’s portrait has become a bit sharper, revealing a study in contrasts that has captured the world’s undivided attention.

Why Kim Jong Un?

As a child, Kim was impetuous and competitive to a fault, according to a 2003 memoir by the family’s former sushi chef, writing under the pseudonym Kenji Fujimoto. The book offered a rare peek into one of the world’s most secretive and consequential families. Kim Jong Il adored his tempestuous son, according to Fujimoto, perhaps seeing in him the steely resolve that has kept the family firmly in control of the pariah state since its creation in 1948.

Using a fake name and pretending to be the son of a North Korean diplomat, Kim Jong Un in 1998 was enrolled in a private school in a sleepy Swiss town, where he spent at least two years. Classmates have been quoted describing him as a good pupil who exhibited an ardent fascination with American basketball — one that extends into adulthood, as evidenced by his hosting of the former NBA star Dennis Rodman earlier this year. In 2000, he vanished from the school without saying goodbye, and little is known about his later teenage years.

Kim Jong Il had been carefully groomed for the role he assumed in 1994. After he suffered a stroke in 2008, succession plans became an urgent priority, North Korean analysts say, and Kim Jong Un emerged as the front-runner among his siblings.

“Perhaps in choosing the youngest of the three sons to succeed him, Kim Jong Il was looking for qualities that he did not have: an outgoing personality,” said Victor Cha, director of Asian studies at Georgetown University and a former senior official on the White House’s National Security Council.

The ailing Kim Jong Il probably saw something more in his handpicked successor, said Ken E. Gause, a senior researcher at Alexandria-based CNA Strategic Studies who has cultivated an encyclopedic knowledge of the Kims.

“Kim Jong Un showed a type of leadership and toughness that his older brothers didn’t have,” Gause said. “That leadership and toughness is required for leadership in North Korea, where, unless you have the personality to play the game, the politics can eat you up really quickly.”

Before he began appearing at official functions, the government spent months shaping Kim Jong Un’s image in an apparent effort to emulate his grandfather, known as much for his charisma as the iron fist he used to build a police state. That endeavor, detailed by defectors, included feeding the prospective leader a carbohydrates-rich diet to make him corpulent and round-faced. Kim soon sported his grandfather’s iconic box-cut hairstyle, with a neatly pressed wave, and began wearing the founder’s trademark dark, Mao-style suits.

After struggling two decades to get Pyongyang to abandon its nuclear program and join the international community, Washington was cautiously optimistic about the young leader, wondering whether his time in Europe might have made him more prone to engagement with the West.

“There was some hope out there,” said Joseph DeTrani, a former CIA and State Department official who negotiated with the North Koreans and has studied the Kim dynasty closely. “He inspired some hope.”

Days after Kim Jong Il’s state funeral on Dec. 28, 2011, North Korea signaled a willingness to negotiate with the United States — but the conciliatory posture soon yielded to confusion. North Korea watchers wondered whether a power struggle was playing out behind the scenes of an outwardly smooth transition.

Still, during his first months in power, Kim Jong Un took on a highly visible role, a stark change compared with his reclusive father. His status was quickly bolstered with titles that conveyed that Kim was in control of the armed forces and the communist Worker’s Party, an ascension to full authority far quicker than his father’s.

The new leader became a fixture of government propaganda videos, which are aired domestically and uploaded on the Internet. Trailed by doting, crusty generals, Kim was shown rallying star-struck troops in the field and planning attacks on the United States in a war room.

He also was portrayed as keen to show a different side of his country, which is notorious for its brutal labor camps and millions of malnourished citizens.

The gregarious statesman was shown touring improbably modern venues in Pyongyang, including a fitness center and a lavish floating restaurant. This past summer, apparently on a whim, he invited dignitaries, including a British diplomat, to ride a roller coaster at a new amusement park.

Unlike his father and grandfather, Kim has made his wife, Ri Sol Ju, a public figure, taking her to events where they are photographed clapping and smiling.

“Kim Jong Un is a much better politician than his father,” said former New Mexico governor Bill Richardson, who has been invited to North Korea on official visits. “He gives better speeches and seems more naturally at ease with people in his greetings and his physical movements.”

Richardson, who has not met Kim on his visits, speculated that the recent flare-up probably has one main audience.

“He wants the approval of the North Korean military,” he said. “He’s trying to convince them that he is ready to govern. There may have been some doubts because of his youth and the fact that he never served in the military, so he’s trying to show them that he’s tough.”

Military pushback?

If factions of the military are uneasy, experts said, Kim has given them more reasons to be unsettled than simply his youth. Last April, he startled observers by acknowledging the failure of a satellite launch — a mission intended as a show of military prowess that could one day threaten the continental United States. Such admissions are unheard of in a country where citizens place a premium on saving face and display nothing but adulation for the military.

Later that month, Kim delivered a landmark speech that some interpreted as a notable departure from his father’s doctrine, known as “songun,” or “military first.”

North Koreans should no longer have to “tighten their belts,” he proclaimed, and could look forward to enjoying “the wealth and prosperity of socialism as much as they like.” Soon after announcing that vision, Pyongyang offered hints that the country was experimenting with modest yet significant agricultural reforms that appeared designed to liberalize the economy a notch.

“There may have been a major pushback from the military,” said Gause, the CNA researcher, noting that, in July, Ri Yong Ho, the chief military officer outside the Kim family, was publicly ousted. His dismissal was part of a broader purge of defense leaders that some analysts believe represents an effort by Kim to surround himself with loyalists.

If Kim is in fact interested in reforms, he might be taking a calculated gamble that by raising the specter of bloodshed, a war-weary United States might be prodded to provide him with a pathway out of the strict sanctions that have helped turn North Korea into the world’s most isolated country.

“Kim Jong Un is making an effort to have a better negotiating position with the U.S. and South Korea,” said Park Hyeong-jung, a senior researcher at the Korea Institute of National Unification in Seoul. “North Korea stands to lose or win.”

Hassig, the defense analyst in Alexandria, said Kim is playing a dangerous game, comparing him to “a puppy” that is “not trained or groomed and thus not afraid of anything.”

The deepest insight into the young leader’s thinking, North Korea experts reluctantly note, may come from the account of the only American he is known to have met: Rodman, the colorful former basketball star who traveled to Pyongyang this year.

“He wants [President] Obama to do one thing: call him,” Rodman said in an interview with ABC News about his late-February trip. “He told me, ‘If you can, Dennis — I don’t want to do war. I don’t want to do war.’”

Yoonjung Seo in Seoul contributed to this report.