Bahk Eun-ji has been with The Korea Times since 2012, building a career across multiple desks. She began at the Business Desk, where she conducted in-depth interviews with key figures in Korea's corporate world. Later, she moved to the Politics & City Desk, focusing on education policy and social affairs. She later served as team leader of the digital content team, leading curation efforts on the newspaper’s homepage and reshaping print stories for social media audiences to enhance digital reach. Now back on the Politics Desk, she covers the National Assembly and the Ministry of National Defense, with a renewed focus on political developments.
EXPLAINER What Korea’s 'quasi-fourth service' means for the Marines
Marine Corps Commandant Joo Il-seok, right, attends a press briefing on the Marine Corps’ transition to a quasi-fourth service system at the Defense Ministry briefing room in Yongsan, Seoul, Dec. 31, 2025. Yonhap
By Bahk Eun-ji
Why Marine Corps’ command structure, mission are being redefined
Korea’s Marine Corps is undergoing a structural overhaul often described as a shift toward a “quasi-fourth service” system — a term that suggests elevation, but not full independence.
The reform does not create a new military branch alongside the Army, Navy and Air Force. Instead, it redefines how the Marines are commanded and what responsibilities they formally carry out, while keeping them institutionally within the Navy. Defense officials say the goal is to correct a long-standing imbalance between authority and responsibility, rather than to expand the force or alter Korea’s joint command system.
At the center of the change is operational control — who commands Marine units in peacetime and who is responsible when crises arise.
Long-standing command imbalance
Although the Marine Corps Headquarters was reestablished in 1987, its main combat units have not been under full Marine control for decades. Since 1973, the Army has had operational control of the 1st and 2nd Marine Divisions, leaving the Marine Corps with administrative authority but limited command over its own frontline forces.
When announcing the reform late last year, Defense Minister Ahn Gyu-back described the change as a historic correction.
“Today can be described as the day the Republic of Korea Marine Corps is reborn,” Ahn said during a policy briefing. He defined the quasi-fourth service system as keeping the Marines under the Navy while granting the Marine commandant “a level of command and supervisory authority equivalent to that of the chiefs of the other services.”
Under the plan, operational control of the 1st Marine Division — currently overseen by the Army’s Second Operations Command — will be returned to the Marine Corps by the end of 2026. Control of the 2nd Division will follow by 2028.
“We will return operational control of the Marines’ key units to the Marine Corps for the first time in 50 years,” Ahn said, adding that the transition would be managed carefully to ensure there are “no gaps in military readiness.”
The reform also includes plans to promote a Marine officer to four-star general and to review the creation of a separate Marine operations command. Ahn said the changes are intended to ensure that the Marine commandant carries responsibilities and authority that are “equal to those of other service chiefs.”
Defense officials emphasize that the Marines will remain part of the Navy for administrative purposes. “This is not separation,” Ahn said. “It is about restoring balance between responsibility and command.”
Marine Corps troops carry out a coastal surveillance mission at sunset on Mal Island, a frontline island in the West Sea, Dec. 31, 2025. Courtesy of Marine Corps Headquarters
Beyond amphibious operations
The reform is also linked to a wider reevaluation of the role of the Marine Corps.
Under current law, the Marines’ role is largely limited to amphibious operations. In practice, however, they have long performed a wider range of tasks, including defending frontline islands, maintaining readiness in the West Sea and serving as a rapid-response force.
Ahn said the government plans to revise the Act on the Organization of the Republic of Korea Armed Forces to reflect this. “We will clearly state in law that the Marine Corps is responsible for amphibious operations and island defense as a national strategic mobility force,” he said, adding that related force enhancement measures would be pursued in parallel.
A study based on in-depth interviews and published in a journal of the Defense Agency for Spiritual & Mental Force Enhancement found that Marines strongly identify with values such as toughness, loyalty and commitment. It also noted that organizational identity must evolve alongside changing missions, warning that rigid institutional roles can hinder the ability to adapt to new security environments.
Security analysts say the debate mirrors similar discussions within the U.S. Marine Corps, which has restructured its forces in response to threats such as drones and missiles, as well as contested maritime environments.
Eom Hyo-sik, secretary general of the Korea Defense and Security Forum, said the reform should be understood primarily as an effort to clarify responsibility.
“Granting greater authority also means accepting clearer accountability,” he said. “If the Marine Corps gains operational control, it must also bear direct responsibility for outcomes.”
However, Eom cautioned that organizational reform alone does not change how wars are fought.
“What ultimately matters is how the Marine Corps defines its role and prepares for future conflict,” he said, adding that the reform should be followed by sustained discussion of doctrine and force design.
Kim Min-seok, a research fellow at the forum, said the quasi-fourth service framework should not be understood as a simple expansion of the Marine Corps.
“Without a clearly defined operational concept, changes in rank and organizational structure risk remaining largely symbolic,” he said.
The entrance to the Marine Corps’ 1st Division in Pohang, North Gyeongsang Province, is seen, Dec. 31, 2025. The slogan “Young men, join the Marines” is displayed at the gate. Yonhap
Realignment, not independence
Defense officials have repeatedly emphasized what the reform is not. It neither creates a new military branch nor dismantles Korea’s joint command structure. Given that demographic decline is already shaping force planning, full separation was never a realistic option, officials say.
Instead, the reform is framed as a realignment, bringing authority, responsibility and mission definition into closer alignment. For the Marine Corps, this means regaining operational control of its divisions and having a clearer voice in joint planning.
As one Marine official put it, “Much may look the same at first. But structurally, the question of who decides — and who answers — is changing.”