How Kim Jong Un's early childhood set him up to become North Korea's ruthless leader

Though North Korea has been under the dynastic rule of the Kim family since the close of World War II, Kim Jong Un, the country's current leader, was never promised the throne after his father's death.

According to Evan Osnos' new report in the New Yorker, Kim rose to power mainly through "attitude and aggression" and displaying an "inner strength" from an early age.

His half brothers Kim Jong Nam and Kim Jong Chol tended towards playfulness and meakness, but Kim Jong-un would wear Soviet military uniforms to his birthday as a child, according to Osnos.

Even at a young age, Kim displayed a temper that may have translated into competitiveness on basketball courts in Switzerland, of all places.

"He was competitive at sports. He didn't like to lose, like every one of us. For him, basketball was everything," João Micaelo, one of Kim's former classmates at a school Kim attended in Bern under a psuedonym during the 1990s, told Osnos.

While his father Kim Jong Il presided over a massive famine where millions perished and suffered malnutrition, Kim fell asleep with a basketball in his bed and was a fan of the Chicago Bulls NBA team.

So when Kim Jong Il passed away in 2011, Kim became the natural choice, who proved even more vicious than his father.

"With Kim Jong Un, he has never yet bitten more than he can chew. Whatever he sets his sights on he gets. He keeps pushing, and pushing, and pushing. We don't know where his brakes are, and I suspect he doesn't know where he can stop," Alexandre Mansourov, the former Soviet diplomat to North Korea told Osnos.

Under Kim Jong Il, North Korea had more open relations with the outside world. He entertained former Secretary of State Madeline Albright in Pyongyang and hoped to improve relations with the US.

But Kim Jong-un quickly became revered for his physical resemblance to Kim Il Sung, his grandfather and the country's founding leader, and he exhibited a brutality not seen under his father's rule.

He had his uncle killed, possibly to thwart an attempt at installing Kim Jong Nam, his half-brother, in a coup. Kim carried out violent purges of top officials with ties to China and insulated himself and his regime.

Evan Medeiros, President Obama's chief Asia adviser, contrasted the two leaders, saying the father's "approach to managing élites appeared to be more incentive-based than coercion-based, making sure that they all got goodies and spoils. The son's approach appears to be 'If you screw with me, I'm just going to kill you-and I'm going to kill you in a really nasty way.'"

Since Kim took power in 2011, North Korea has tested missiles at a blistering rate, testing more times than his father and grandfather combined. Of six total nuclear tests, four have occurred under Kim Jong-un's watch.

Today, Kim's North Korea stands on the verge of full, unquestionable nuclear capability and tensions with the US stand near all-time highs. Though experts assess Kim intended to secure his regime against foreign invasion by building nuclear weapons, not a soul on earth can truly say what he will do with full nuclear powers.

Read the full New Yorker article here.