Who is Kim Jong Un and what will he decide to do?

If North Korea goes ahead with its threat to fire ballistic missiles toward the U.S. territory of Guam, the order will come from Kim Jong Un himself.

The officials in charge of North Korea's missile program could complete their preparations by next week and would then wait for the 33-year-old leader to decide what to do next.

Will Kim give the order to fire, potentially inviting retaliation from an American president who has his military "locked and loaded"?

This is not a question of technical capability. North Korea has already demonstrated that it has made great advances in its missile program and can theoretically now hit the U.S. mainland.

No, this is a question of strategy.

"The North Koreans have been very clear that they need his authorization. This is a moment for Kim Jong Un," said Michael Madden, who runs the North Korean Leadership Watch website and closely studies Kim. "He may take it as an opportunity to prove himself, or as an opportunity to let cooler heads prevail."

The Kim regime has a history of making bellicose threats that it cannot or does not make good on. This may well be one of those cases.

Or it might not. For starters, North Korea likes to mark important dates, and there are two approaching.

On Tuesday, North Korea will celebrate Liberation Day, marking the end of colonial rule by Japan, over which any Guam-bound missile would fly. Then on Aug. 21, South Korea and the United States will start annual military exercises that always antagonize North Korea.

The problem with trying to figure out what Kim might do in a situation like this is severely complicated by the fact that the outside world knows almost nothing about him.

He was born in North Korea in 1984, the youngest son of Kim Jong Il - who would become the country's leader a decade later - and a Japanese-born ethnic Korean dancer named Ko Yong Hui.

The fact that he was the third son should have disqualified him from contention for the leadership in a society where the firstborn son has primacy.

But thanks in no small part to his mother's ambition, Kim Jong Un soon became heir apparent. He was anointed successor at the age of 8, his aunt, Ko Yong Suk, told The Washington Post last year. He was given a general's uniform decorated with stars, and real generals with real stars bowed to him from that moment on.

"It was impossible for him to grow up as a normal person when the people around him were treating him like that," said Ko, who, before defecting to the United States in 1998, acted as Kim's guardian while he went to school in Switzerland.

When he was 12, in 1996, Kim started school in Bern, the Swiss capital, and lived with his aunt and uncle and his older brother Kim Jong Chol in an ordinary apartment.

Kim's mother used to visit regularly, and intelligence services kept close tabs on her, the Swiss newspaper Le Matin Dimanche reported last month. But the government forbade them from spying on the children: Jong Chol, who agents called "the tall skinny one," and Jong Un, "the short fat one."

As a result, Swiss intelligence had little information on the boy who would become the supreme leader of North Korea.

Instead, much of what the world knows about Kim as a child comes from Kenji Fujimoto, the idiosyncratic Japanese sushi chef who, down on his luck in the 1980s, moved to North Korea to serve fish to Kim Jong Il.

In interviews with The Post, Fujimoto described the way Kim, who was then a child, refused to shake Fujimoto's hand or use polite forms in Korean.

Fujimoto recalled the day when Kim, who was about 10, had a tantrum at being called "little general" and instead insisted on being called "comrade general." "This is an unforgettable episode that showed the aggressive side of his personality," Fujimoto wrote in one of his books.

The other tales from Kim's teenage years reveal a boy who was spoiled - he had the latest PlayStations and Air Jordan shoes - and competitive, his former classmates have said.

"For him, basketball was everything," Joao Micaelo, one of Kim's classmates, told CNN in 2010. "He played basketball, he had basketball games on his PlayStation. The whole world for him was just basketball all the time."

But after Kim returned to North Korea in 2001, the trail - such as it is - runs out.

Kim is thought to have attended Kim Il Sung Military University in Pyongyang and to have started being groomed for his eventual role.

On Jan. 8, 2009 - Kim's 25th birthday - Kim Jong Il announced to his cadres that he'd chosen his youngest son as his successor. But the heir apparent was not seen in public until Oct. 10, 2010, at a Workers' Party celebration where he stood next to his father on the balcony overlooking Kim Il Sung Square. It was his coming out.

He was rapidly promoted up through the Workers' Party and military ranks as his father's health deteriorated. When his father died of a heart attack at the end of 2011, the "Great Successor" was ready to take over.

Since then, Kim has defied hopes that his Western education would make him a reformer. Instead, he has presided over a system every bit as brutal as his father's and grandfather's.

He has had his uncle, Jang Song Thaek, and at least 150 high level officials executed, the South Korean intelligence service estimates, and many more purged.

Kim is also blamed for the gruesome death of his half brother, Kim Jong Il's firstborn son and therefore a potential rival, this year. Kim Jong Nam died soon after having his face smeared with a chemical weapon in a Malaysian airport terminal.

He has also tried to seal the country more tightly, cracking down on border crossings and finding new ways to block outside information from getting in.

And, most alarmingly, Kim Jong Un has made observable progress on his vow to acquire an intercontinental ballistic missile capable of reaching the United States. In his Jan. 1 New Year's address, Kim said his rocket scientists were in the final stages of preparations for a test.

Then, on July 4 - a date that was no coincidence - North Korea fired an ICBM with the technical capability to make good on that threat. At the end of the month, it fired another one.

At a huge celebration banquet in Pyongyang last month, the comrade general said the launches were "a remarkable leaping forward in the great era of Kim Jong Un and its inexhaustible potentiality and the invincible stamina of heroic Korea."

But beyond the childhood accounts and the reports about Kim in his regime propaganda, very little is known about him as a person or as a leader.

He has not traveled abroad or hosted a foreign leader since he was designated successor in 2010, and the only Americans who have met him are retired basketball star Dennis Rodman and his entourage.

"I think people don't see him as . . . a friendly guy," Rodman told ABC after returning from his fifth trip to Pyongyang, in June, although he did not meet Kim this time.

"If you actually talk to him," you see a different side of Kim, Rodman said. "We sing karaoke. It's all fun. Ride horses, everything," said the former Chicago Bull - Kim's favorite team.

Because the previous two North Korean leaders traveled and met outsiders, psychological profilers were able to build a picture of them. But the lack of human intelligence on Kim means that the CIA hasn't even been able to write a proper profile of him, said Madden of North Korea Leadership Watch.

A South Korean expert who advises the government in Seoul said Kim displays some "narcissistic personality traits."

"He believes that the whole world revolves around him, so he exaggerates and overrates himself," said the expert, who did not want to be named because of the sensitivity of his work. "His intelligence, power, success - it's all a fantasy."

And, like any narcissist, Kim wants to remain the center of attention.