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His comments this week indicated there would be little change to major policies laid out by Kim Jong-un’s father in the three years before his death. Mr. Yang said the new leader was focused on a “knowledge-based” economy and looking at economic reforms enacted by other nations, including China.

The North increasingly has looked to China for guidance on how to revitalize its moribund economy, particularly as South Korea, Japan and other nations have frozen trade and aid to the North amid concerns about its nuclear ambitions.

Little is known about Kim Jong-un’s background and experience, though North Koreans have been told he studied at Kim Il-sung Military University and was involved in military operations such as the November 2010 artillery attack on a South Korean island that killed four South Koreans.

Earlier this month, North Korea’s state-run broadcaster aired a documentary about the new leader that began filling in some blanks from before his public debut.

The footage shows him observing the April 2009 launch of a long-range rocket and quotes him threatening to wage war against any nation attempting to intercept the rocket, which North Korea claimed was carrying a communications satellite but the United States, South Korea and Japan said was really a test of its long-range missile technology.

It was the first indication of his involvement in that controversial launch.

Yet if Kim Jong-un was playing a prominent behind-the-scenes role before 2010, his training period would have been much shorter than that of Kim Jong-il, who spent 20 years working under his own father, Kim Il-sung. Even after his father’s death, Kim Jong-il observed a three-year mourning period before formally assuming leadership.