Since the signing of an armistice agreement between North Korea, China, and the United States in 1953, after three years of vicious fighting, South Korea, aka the Republic of Korea (ROK), has remained technically at war. After early attempts to establish democracy and market-oriented economics, there was a military coup in 1960, led by General Park Chung-hee, who was remarkably successful in developing the South Korean economy but also suppressed all civic freedoms.
This authoritarian style of government continued under General Chun Doo-hwan, who came to power by assassinating Park. Chun had attended the Korea Military Academy, then as now South Korea’s premier military training institution. Since his time there, this institution has remained a bastion of conservative politics and the linchpin of ROK Army control of the military – a powerbase sometimes referred to as “One Team.” Chun is notorious for the brutal suppression of the Gwangju Uprising on May 18, 1980, in which many hundreds of democratic protesters were killed, and thousands wounded.
South Korea has subsequently made remarkable progress in building a stable and prosperous democracy, but South Koreans remain understandably sensitive about any perceived threat to the hard-won civilian control of the military.
The appointment of senior generals and admirals is therefore a matter of great importance, specifically for the heads of the three services – the Army Chief of Staff, the Chief of Naval Operations (CNO), and the Air Force Chief of Staff – together with the chair of the Joint Chiefs of Staff (JCS). These appointments are chosen by South Korea’s president.
The military is constitutionally neutral, so experience and competence ought to be the primary characteristics used to determine promotions. In practice, however, it has recently become more common for incoming presidents to assert their political influence in this sphere, and this politicization is seen by many commentators as unwelcome. The traditional dominance of the Korea Military Academy, and of the ROK Army, from whose ranks the JCS chair is usually chosen, is especially pertinent to this issue. The JCS has peacetime authority for operational decisions, and is ultimately responsible for maintaining and enhancing the combat capabilities of the four independent services, as well as overseeing the development of next-generation platforms and systems.
The political neutrality of the South Korean military has been cast into doubt by the sudden and irregular declaration of martial law during the night of December 3, 2024. President Yoon Suk-yeol’s action, for which he was impeached and is now under criminal investigation, seems to have been aided and abetted by his close ally, Lt. General Kim Yong-hyun (at the time the the minister of national defense), and also, directly or indirectly, by many other ROK Army generals in important roles, all of whom graduated from the Korea Military Academy. These military leaders are alleged to have played an unconstitutional and/or illegal role in what many have interpreted as an attempted military coup.
The general public is greatly disturbed that South Korea is now on a slippery slope, which could ultimately lead to a return to the bad old days of military dictatorship. Moreover, this apparent involvement of the South Korean military in domestic political affairs has seriously undermined their reputation for ethical and professional conduct, and also impacted their status as one of the best operational combatant forces in the world.
South Korea’s New Military Brass
With the inauguration of President Lee Jae-myung on June 4, it was widely expected that the leadership of the South Korean military would be reviewed, for several reasons. First, because of the involvement of many senior generals in the martial law implementation, by sending or deploying troops for dubious purposes; second, to demonstrate that Lee is firmly in control of the military; and third, to reduce the influence of the Korea Military Academy, and the dominance of the ROK Army. Ideally Lee should reestablish institutional neutrality among the armed forces, but at the least he needs to ensure their loyalty.
On September 1, Lee reshuffled the seven most senior ranks of four-star military leaders, promoting three-star generals and admirals. Besides the four members of the JCS, he also replaced the deputy commander of the ROK-U.S. Combined Forces Command (CFC), and the heads of Ground Operations Command and 2nd Army Operation Command. Lee has retired all the existing four-star officers, choosing to promote three-star generals and an admiral to form his new military leadership. Perhaps he also expects some degree of personal loyalty from them, in return for these promotions.
This is the second time that such a clean sweep of the top brass has occurred. In May 2022 then-President Yoon Suk-yeol replaced the existing military leaders with a team considered to be more politically conservative. This was much criticized at the time as political interference in the day-by-day operations of the ROK Armed Forces, and detrimental to their essential role in deterring North Korea threats.
Lee is known to believe that the decision-making processes of the JCS, the Ministry of National Defense, and the Defense Acquisition Program Administration (DAPA) are too reliant on input from the army. It is no surprise then, that he has attempted to rebalance the influence of the independent services, selecting several officers who are not graduates of the Korea Military Academy. Lee also appointed an air force officer as chair of the JCS: Jin Yong-sung, who led the Strategic Command, established in 2024, as its inaugural chief.
It is conspicuous that some of the new appointments do not adhere to long established traditions governing which roles officers should serve in before being promoted to the upper echelons. Neither the newly appointed JCS, Jin Yong-sung, nor the CNO, Admiral Kang Dong-gil, have commanded operational combat units, which appears to be unprecedented. All of Kang’s previous roles have been administrative: in personnel, intelligence, logistics, force improvement planning, and naval policy.
Lee’s military reshuffle may have been influenced by the big changes occurring in the U.S. military under President Donald Trump. He may have wanted to select South Korean generals and admirals with good presentational skills, giving less weight to the need for combat experience. Lee has commented on the current military tension between North and South Korea, emphasizing the need to avoid conflict.
Implications for South Korea’s Military
Among the challenges facing South Korea’s new military leadership are the Chinese military expansion into the Yellow Sea, and the renewed closeness of relations between China and North Korea. However, the most urgent task is to attempt to revive the Comprehensive Military Agreement between two Koreas, signed in September 2018 but subsequently repudiated by the North. The success or failure of such efforts will determine whether South Korea’s defense posture should be primarily defensive or offensive. And that decision will determine the planned acquisition of next-generation platforms and systems to contribute toward future CFC capabilities.
The Joint Strategic Objective Plan (JSOP), updated every five years, outlines long-term strategic objectives, concepts, and directions for force development, providing a framework for specific defense programs and acquisition requirements within the military services and the Defense Acquisition Program Administration. When the JCS came from the ROK Army, the ROK Navy had difficulties getting its Force Improvement Plan (FIP) included in the JSOP, but this may change with the appointment of Jin as the new JCS.
Jin may be less supportive of the CVX aircraft carrier, however, since it requires F-35B VTOL stealth aircraft instead of the F-35As that the ROK Air Force prefers. During President Moon Jae-in’s administration, a balanced solution was proposed that satisfied both the ROK Navy and Air Force: the Navy would command the CVX, while a two-star Air Force general would command its carrier air wing. However, this arrangement was lost when Yoon, Moon’s successor, diverted funds to increase the ROK Army’s capabilities for future ground warfare, such as the Tiger Army program.
The new CNO, Kang Dong-gil, spent most of his land assignment formulating the ROK Navy’s future FIP program, which will likely inform future naval development. The first item on his agenda will surely be to resolve the dispute between Hyundai Heavy Industries and Hanwha Ocean on who should design the leadership of the KDDX next-generation destroyer. He also needs to persuade the so-far-reluctant U..S. Navy that the next batch of the Jang Bogo–class submarines (KSS-III) should be nuclear-powered. The United States has already authorized joint production of nuclear–power submarines for the Royal Australian Navy.
The outgoing CNO, Admiral Yang Yong-mo, focused on unmanned vehicles under a concept called the “Navy Sea Ghost” with so-called fourth industrial revolution technologies. He failed to get any new platforms included in the JSOP program. Worse, Yang is now embroiled in a corruption scandal involving the management of the ROK Navy Hotel.
The South Korea-U.S. Alliance
Lee met Trump in Washington on August 25, 2025, without a lot to show for it, though he will probably be happy simply to have avoided disaster. During the summit, the slogan “Make American Shipbuilding Great Again” (MASGA) was used to emphasize cooperation between South Korea and the United States in one area where they are in complete agreement: the need to restore U.S. naval and commercial shipbuilding capacities to compare with China’s remarkable expansion of its shipyard facilities.
On the downside, South Korea fears being exploited by Trump, forced to contribute investment and expertise without much commercial return. And from a security perspective, MASGA may impact the ROK Navy and Korea Coast Guard requirements for future shipbuilding. On the upside, however, MASGA should help deflect Trump’s mercurial and vindictive behavior away from South Korea by providing a bargaining chip in moderating tariffs on semiconductors and cars, without South Korea having to open up too much to imports of U.S. agricultural products.
The Trump administration is also keen for South Korea to increase its defense budget, having been reported as suggesting a figure of 3.8 percent of GDP, considerably above the current 2.3 percent. In response South Korea’s Ministry of National Defense has requested an 8.2 percent year-on-year increase. The Lee administration has yet to determine how to allocate this increased defense budget, and may face political difficulties from supporters of the different military services.
The United States places great importance on trilateral naval cooperation against North Korean nuclear and missile threats, which implies closer military coordination between South Korea and Japan. The Yoon administration made significant moves in this direction, and so far, it seems that the new Lee administration will not renege on these commitments, though it may well be reluctant to take any further steps.
It has been reported in the Japanese press that the Japanese Ministry of Defense has submitted a proposal to the United States that East China Sea (including Taiwan), the South China Sea, and the Korean Peninsula should be treated as a single military theater. The plan is explicitly aimed at resisting China, and would therefore be deeply problematic for any Korean administration.
There are ongoing discussions between Washington and Seoul about alliance modernization, and the U.S. understands this to include an expanded geographic and functional scope. It is anticipated that United States Forces Korea (USFK), instead of just being a garrison deployment, will be more expeditionary, and the U.S. will exercise its “strategic flexibility.” This means not only focusing on deterring the threat from North Korea, but also using USFK ground forces, and some assets deployed to South Korea, to contribute toward solving regional crisis and contingencies. This would include the Taiwan Strait and the South China Sea. The U.S. decision to move some Patriot missile interceptors from South Korea to the Middle East earlier this year seems to confirm this new approach, though the U.S. has pledged to deploy more advanced and powerful assets to Korean Peninsula as necessary and appropriate, to maintain the capabilities of USFK.
As for Seoul’s contribution toward alliance modernization, some observers expect Lee to propose a massive new investment for the ROK Armed Forces. This could include the CVX aircraft carrier, new hypersonic missiles, nuclear-powered submarines, and revolutionary unmanned vehicles relying on AI. He has already agreed that the increased 2025 defense budget will be allocated to enhance the Korea Triad System, acquiring SM-3 interceptor missiles operating between 90 km and 150 km, and speeding up the development of indigenous L-SAM missiles.
Some on the left of Lee’s Democratic Party feel, however, that the alliance goalposts are being moved, perhaps too rapidly and too unpredictably. They have argued that South Korea’s military was being too ambitious during the Yoon administration, taking on too much risk in relying on untested advanced technology. According to this view, Seoul’s defense policy and military strategy should now be recalibrated, taking a more moderate approach to defense reform. This could mean reconsidering the CVX program for an indigenous aircraft carrier. Instead, some advocate building more small and speedy platforms copied from the U.S. Marine Corps Littoral Regiment, together with small fast landing craft to conduct island-hopping operations.
Lee’s Approach to the Military
Lee Jae-myung faces many challenges. He must steer a course between the two great powers, finessing the outrageous demands from Trump while not offending China’s Xi Jinping. Then there is North Korea’s declaration in 2022 that it is a nuclear-armed state. Lee’s diplomatic policy is characterized as “pragmatic diplomacy based on the ROK’s national interest,” but what does this tell us about the ROK’s future defense policy and military strategy?
It is rumored that Lee has been working sedulously to build support among the ROK Armed Forces, advocating a balance among the independent services and for a politically neutral stance to become conventional for all senior officers. This reshuffle of the top brass seems to exemplify these principles.
It is clear that Lee wants to be reduce the dominance of the ROK Army, and also lessen the influence of graduates of the Korea Military Academy. He wants the ROK Navy and Air Force to take up a more central role in the combined defense posture against North Korea.
The incoming JCS, Jin Yong-sung, will surely be pleased to follow the president’s lead, and hopefully will enhance South Korea’s capabilities in the air and sea domains, breaking free from 70 years of rigid adherence to a philosophy that sees the land domain as all-important.