Kim Jong-un is the supreme leader of North Korea, the third and youngest son of Kim Jong-il (1941–2011) and the grandson of Kim Il-sung (1912–1994). Following his father's death in 2011, he was announced as the "Great Successor" by North Korean state television. He has held the titles of the First Secretary of the Workers' Party of Korea, the Chairman of the Central Military Commission, First Chairman of the National Defence Commission of North Korea, the Supreme Commander of the Korean People's Army, and also a presidium member of the Central Politburo of the Workers' Party of Korea.
North Korea's economic co-operation with China will suffer for Jang's ouster
Sonny Lo believes military hardliners succeeded in winning Kim's ear in deadly power struggle
Two years after the death of Kim Jong-il, the power struggle in North Korea between military hardliners and the more moderate pro-Beijing faction led by Jang Song-thaek has become so serious that Jang not only lost the battle but his life as well.
Even before Jang was ousted and executed for his various "crimes", there were already signs that the military hardliners led by Choe Ryong-hae, a vice-marshal of the armed forces and the military's top political officer, was gaining the upper hand. In May, as a special envoy of Kim Jong-un, Choe visited China and met President Xi Jinping , telling Xi that North Korea cherished its relations with China, and that it was willing to co-operate to solve issues through the six-party talks on the denuclearisation of the Korean peninsula.
In the days after Jang's execution, Choe has appeared in official photos and was often pictured next to Kim Jong-un, demonstrating that he is now seen as second in command.
Jang was promoted in June 2010 to vice-chairman of the National Defence Commission, where he was expected to bolster Kim Jong-un's rise to succeed the ailing Kim Jong-il. Members of Jang's faction were also promoted to ministerial positions.
The rise of Jang's faction cost another its influence, however. There were rumours that the traffic accident that killed Ri Je-gang, a senior Workers' Party director, was orchestrated by Jang. Ri had reportedly been involved in a previous power struggle aimed at ousting Jang.
The sudden death of Kim Jong-il - two years ago - led to an even fiercer power struggle between Jang and the military hardliners, who sought to become Kim Jong-un's trusted lieutenants.
Prior to Kim Jong-il's death, he had told Chinese leaders during his visits between 2010 and 2011 that the old North Korean leaders aged over 70 should retire earlier so as to clear the way for his son, Jong-un's, succession. That implied even Jang would have to retire; however, Kim's death meant the plan was not realised.
As a liberal-minded reformer, Jang had long argued for a more open-door policy, which North Korea adopted in 2006, when he accompanied Kim Jong-il on a visit to Shanghai. However, Jang's advocacy for the Chinese reform model was opposed by military hardliners. His influence was curbed until 2008, when Kim Jong-il suffered a stroke and designated him to assist Jong-un in the leadership succession.
However, Kim Jong-un did not appear to trust Jang. It was rumoured early this year that Kim was fully protected by military officers whenever he visited various places because he had been the target of an assassination plot in November last year. The special military tribunal that tried and convicted Jang for treason criticised him for plotting against Kim Jong-un and trying to overthrow him.
Pyongyang's official Korean Central New Agency published a long article detailing Jang's transgressions, which included "unwillingly standing up from his seat and half-heartedly clapping" when Kim received an important title.
State media also accused Jang of unpatriotically selling off the land of the Rason economic and trade zone to a foreign country for five decades. This referred to his liberal-minded, open-door policy towards China. From the hardliners' perspective, North Korea should have handled matters in the zone rather than being economically dependent on China.
It was clear that Jang's faction had lost out when his confidants Ri Ryong-ha and Jang Su-gil, who both held high-level posts in the Central Administrative Department of the Workers' Party, were executed.
Even though Jang's wife, Kim Kyong-hui, is the sister of Kim Jong-il and aunt of Kim Jong-un, Jang's extramarital affairs embarrassed the family and ultimately led to his downfall.
Rumours of pornographic videos featuring Jang with members of the Unhasu Orchestra added fuel to the fire and gave additional weight to his "criminal" activities.
Personal rule in North Korea means Jong-un succeeded his father without a power base but with the support of his elderly uncle. Yet Jang's more moderate leanings put him at odds with military hardliners, and to them he had to be removed.
Doing so has paved the way for them to become the unquestioned lieutenants who support the supreme leader.
In this case, Kim Jong-un naturally sided with the military hardliners and ousted the politically ambitious Jang.
The implications for China and the Korean peninsula are obvious.
While China remains an ally of North Korea, the military hardliners in Pyongyang will not adopt the Chinese open-door policy, opting instead for a more gradual approach to economic reform.
The Korean peninsula, meanwhile, will continue to be the scene of North Korean shows of military strength and power.
Personal rule means sudden and unpredictable political moves will continue to surprise other countries.
Sonny Lo is professor and head of the department of social sciences at the Hong Kong Institute of Education