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 Gause, a senior researcher at Alexandria, Va.-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.