SEOUL, South Korea -- When Kim Jong Un became leader of North Korea two years ago, he was surrounded by advisers who were two and, in some cases, nearly three times his age. Most had decades of experience in the Workers' Party or military. Two were members of Mr. Kim's own family.
But rather than lean on that support team, Mr. Kim has instead sought to dismantle it, using a series of demotions and purges to grab power almost solely for himself. North Korea on Friday announced the execution of the most prominent of Mr. Kim's advisers, Jang Song Thaek, accusing him of opposing Mr. Kim's rise and plotting an overthrow.
The pace and brutality of Mr. Kim's attempted power consolidation far exceeds what analysts expected and carries significant consequences for the region and the United States. If Mr. Kim can indeed lock down power, one of the world's most secretive and repressive nations may continue as it is for decades. If Mr. Kim fails, a 65-year run of family rule could face resistance, and a nuclear-armed nation could plunge into chaos.
For now, there are no outward signs of instability in the North, and it's unclear whether Jang's execution marks the last stage of Mr. Kim's ascendancy or the first hint of opposition. In Jang's execution -- documented on the front page of North Korea's state-run newspaper -- some analysts see a Stalin-style warning sign sent to other potential rivals, those who feel that Mr. Kim is either too untested or unqualified to run the country.
Mr. Kim is thought to be 30 years old, making him among the world's youngest heads of state. Some who study the North say Mr. Kim, as a product of his age, has felt it necessary to quickly remove those from older generations who owed their loyalty to his father, Kim Jong Il. Well before the purge of Jang, Mr. Kim had ousted scores of second- and third-level functionaries in the Workers' Party and military in one of the North's biggest personnel turnovers in decades.
As a telltale signal of the change, Mr. Kim has removed or demoted five of the seven elderly officials who walked alongside the hearse of Kim Jong Il at a state funeral two years ago. Those officials, dubbed at the time the "Gang of Seven," were described in the South Korean media as the likely backbone of Kim Jong Un's rule. Several in the group knew Kim Jong Il from his college days or before. Their average age at the time of the funeral: 73.
Among the gang, U Tong Chuk, who oversaw the North's secret police, hasn't been seen in public since March 2012, his absence unexplained. Ri Yong Ho, a high-ranking military chief, was relieved of his duties for what the North tersely described as an illness. Two other top officials were demoted. Jang's ouster was by far the most public. The only two who have kept their positions -- Choe Tae Bok and Kim Ki Nam -- are in their mid-80s and represent little threat.
"Kim Jong Un has proven to the nation and his people that he is capable of taking out even those closest to him," said Suh Choo-suk, an expert at the Korea Institute for Defense Analyses in Seoul. Mr. Suh added that the turnover recalls the 1950s and 1960s, when national founder Kim Il Sung purged a group of more moderate challengers with ties to the Soviets and Chinese. Kim Il Sung banished or killed those opponents, replacing them with a hand-picked group of former guerrillas who fought alongside him in northeastern China.
Even for Kim Il Sung, a full consolidation of power didn't come until 1972 -- 24 years after he established the country -- when the North adopted a constitution that authorized his supreme power. The next leader, Kim Jong Il, needed almost as much time to cement his own rise: He was groomed by Kim Il Sung starting in the mid-1970s and gained full control of every major institution in 1998, four years after Kim Il Sung's death.
For Kim Jong Un, the father-to-son power transfer wasn't nearly as well-planned. Kim Jong Il died in 2011, when the succession process was in its infancy and before Kim Jong Un had built up his own network of lieutenants.
As a result, many outside experts and U.S. officials believed that Jang and others -- including Kim Jong Un's aunt, Kim Kyong Hui -- would play key caretaker roles, perhaps with a power-sharing system. That hasn't proven the case. In the months after his father's death, Kim Jong Un received multiple and redundant leadership positions, placing him clearly in supreme command. Though Mr. Kim still might rely on his aunt for guidance, she is thought to suffer from liver problems and is rarely seen in public.
The effect of Mr. Kim freeing himself from his senior advisers remains uncertain. Several Beijing-based analysts and scholars said Friday that they feared that North Korea's relations with China would suffer, as Jang had been a key interlocutor with Chinese officials. Other experts, such as Bruce Klingner, a senior research fellow at the Heritage Foundation, said Mr. Kim has no potential "moderating influence" and might behave more recklessly.
The execution of Jang has also sparked concern that Mr. Kim can act rashly, crossing lines that even his father and grandfather would not have traversed. Though Jang had been stripped of his positions days earlier, Jang was Mr. Kim's uncle, and Kim family members have been safe for decades from execution.
"The way Kim Jong Un dealt with his uncle was very cruel," said Cheng Xiaohe, an expert in North Korean affairs at Renmin University's School of International Studies in Beijing. "He utterly turned back on his own flesh and blood."