Concerns about possible instability in North Korea were raised this week when Vice Marshal Ri Yong-ho, head of the General Staff, was abruptly dismissed. The move smelled of a power struggle. The subsequent announcement that Kim Jong Eun was elevated to marshal—a military rank second only to the "Grand Marshal" bestowed on Kim Il Sung and Kim Jong Il—indicated that he retained the upper hand in the battle for control in Pyongyang.

Last week the news out of Pyongyang provided some amusement and hope for positive change, as Kim Jong Eun was serenaded by Disney characters and other Western cultural icons. That sparked serious speculation that the new leader might be more open to economic and political reform than his late father.

Clearly the North Korean leadership transition is more fraught than previously thought. But what is driving events in Pyongyang remains uncertain. Potential explanations revolve around four Ps—power, parity, people and policy:

• A classic struggle for power between the leader and potential contenders is the most likely explanation. But was Gen. Ri's sudden removal due to a more secure Kim Jong Eun able to purge from the innermost circle to further consolidate his power? Or did it indicate that older elites felt emboldened enough to attack a key Kim loyalist?

• Then there's the issue of parity between the Korean Workers' Party (KWP) and the military. Under Kim Jong Il, power shifted to the military, as the National Defense Commission became the pre-eminent center of government power. But under Kim Jong Eun, the KWP has regained some power. Some experts speculate that the KWP's Central Military Commission could eventually eclipse the National Defense Commission as arbiter of North Korean military policies.

Gen. Ri's dismissal could reflect a struggle for parity between the party and the military. But Gen. Ri had a foot in several competing camps. He was rewarded by both Kim Jong Il and Kim Jong Eun, he was one of Kim Jong Il's pallbearers, and he was—until this week—thought to be the younger Kim's military mentor. Thus, he was a "made" member of both the old guard and the new regime. He also held positions of authority in both the military and KWP. He was a member of the KWP Central Committee Presidium, the party's highest-level body, and co-chairman of the Central Military Commission.

• Rather than a struggle to wrest power from Kim Jong Eun, the purge may instead result from people fighting for closer access to Kim. There are widespread rumors that Gen. Ri was defeated in a struggle with personal rival Choe Ryong-hae, a senior party official.

Gen. Choe also recently became vice marshal, a member of the decision-making KWP Politburo Presidium and vice chairman of the party's Central Military Commission (despite no military experience). During the important 100th anniversary celebrations of Kim Il Sung's birth, Gen. Choe stood at Kim Jong Eun's side, indicating his status had overtaken that of Gen. Ri.

• The least likely explanation for the purge is a debate over policy. Kim Jong Eun's Mickey-Mousing resurrects the discredited theory that a despot's appreciation of Western culture presages an embrace of democracy and market principles. Gen. Ri's removal played into this theory with adherents depicting him as a hardliner striving to obstruct Kim's desire for bold reforms.

Yet there is no evidence that North Korea has become any less dangerous under its new leader. While the junior Kim has displayed a more dynamic and pragmatic image than his reclusive father, his regime, since he assumed power, has called for the assassination of South Korean President Lee Myung-bak and threatened to reduce South Korean media organizations to "ashes in three or four minutes."

Most importantly, Kim violated U.N. resolutions by ordering April's launch of a long-range ballistic missile. Nor should we forget that he oversaw the brutal purges that killed hundreds during the past two years, and he has been credited with masterminding Pyongyang's two acts of war against South Korea in 2010.

There's one thing we know with relative certainty: That Kim Jong Eun felt it necessary to purge Gen. Ri strongly indicates his transition isn't going smoothly. Additional purges and shakeups should be expected. All this is worrisome to the U.S. and its allies, since it increases the potential for provocative acts or, more ominously, the implosion of a regime with nuclear weapons.

Mr. Klingner is senior research fellow for Northeast Asia at the Heritage Foundation. He previously served 20 years with the Central Intelligence Agency and the Defense Intelligence Agency.