The U.S. Marine Corps’ newest rotational force, Marine Rotational Force-Southeast Asia (MRF-SEA), played a key role during Exercise Cobra Gold 2025, which took place in Thailand from Feb. 25 to March 7. Celebrating its 44th year, Cobra Gold is the largest joint and combined exercise in the Indo-Pacific region. This year, the exercise welcomed over 3,000 U.S. personnel, including U.S. Marines from MRF-SEA, and other Marine Corps units including 1st Light Armored Reconnaissance Battalion and 3rd Assault Amphibian Battalion, 1st Marine Division; Marine Aerial Refueler Transport Squadrons 152 and 153, 1st Marine Air Wing; and 9th Engineer Support Battalion, 3rd Marine Logistics Group. U.S. Marines participated in numerous training events, including expert-led training exchanges, engineering civic action projects, as well as field training in various skills, including jungle survival, urban operations, multilateral live-fire ranges, non-combatant evacuation operations, CBRN response and combat casualty care.

Cobra Gold, first held in 1982, was originally aimed at improving coordination between the U.S. and Thai armed forces, both for military operations and humanitarian efforts. Over the years, the exercise has grown in scope and complexity, incorporating civic action projects, staff planning training, and exchanges on jungle survival skills and military tactics across the country. As of 2025, the exercise boasts participation from approximately 30 nations.

MRF-SEA’s participation in Cobra Gold 2025 highlighted the unit’s extensive capabilities in tactical and operational planning, command and control, and versatility as a Marine Expeditionary Unit command element. Coming off the heels of successful iterations of Keris MAREX in Indonesia and Valiant Mark in Singapore, the operations section of MRF-SEA was faced with the task of planning for Cobra Gold underneath the U.S. Army’s operational jurisdiction. This endeavor took extensive coordination and creative thinking as the two branches combined forces to make the exercise a success.

“MRF-SEA assumed the role of the U.S. Marine component command element, requiring significant planning and coordination to ensure the effective training of seven separate Marine units,” said U.S. Marine Corps Maj. Jonathan Turello, assistant operations officer for MRF-SEA. “Command and control of subordinate units and integration with higher, adjacent, and partnered forces is our forte. When we arrived in Thailand, we were able to rapidly establish our command operations center and coordinate the efforts of 300 Marines from I Marine Expeditionary Force, III MEF and Marine Forces Reserve.”

Ahead of the opening ceremony, a detachment of eight USMARFOR Marines from the 3rd Assault Amphibian Battalion, including six crewmen and two mechanics, conducted vehicle inspections and maintenance with their counterparts in the Royal Thai Marine Corps at Camp Jessada in Sattahip. This exchange focused on improving the operability of the Thai vehicles in preparation for the upcoming Cobra Gold Amphibious Exercise (AMPHIBEX).

With only three days remaining until AMPHIBEX, the U.S. Marines discovered that one of the Thai vehicles’ crew vent fan was malfunctioning and wired incorrectly. The mechanics salvaged parts from old fans in storage, replacing the faulty fan, repairing the wiring, and soldering in new harnesses. Additionally, the transmission of a Thai vehicle required a new valve selector solenoid gasket, which the mechanics fabricated and installed. These repairs were just a few examples of the exceptional efforts made by the Marines of 3rd AAB, many of which were beyond the Thai Marines’ technical capabilities and something they would typically outsource to a civilian company.

“Our team was able to get three of our Thai partners’ vehicles back in service, and we even got one to splash for the first time in two years,” said GySgt. Kurt King, Bravo Company Logistics Chief. “We doubled their operational readiness from one squad to two, saving them thousands of dollars. Beyond the mechanical work, we exchanged knowledge and tactics with the Royal Thai and ROK Marines, forging lasting friendships and unforgettable memories.”

The success in the motor pool served as a prelude to the next chapter of the exercise, which would take participants deeper into the jungles of Thailand, showcasing joint and combined interoperability in a new and more primitive environment.

After the exercise’s opening ceremony in Korat, Marines with 1st Light Armored Reconnaissance Battalion, attached to MRF-SEA for Cobra Gold, gathered on the Royal Thai Armed Forces’ infamous Recon Camp to conduct Jungle Survival Training and patrolling with personnel from the Royal Thai Marine Corps and Republic of Korea Marine Corps. The jungle training, which has been a highlight of the exercise amongst Marines for decades, challenged the critical thinking skills of all participants as they learned how to endure the conditions of a dense jungle environment riddled with predatory animals and harsh conditions. It was here where the nations began to form bonds as they worked towards more complex training events like the upcoming AMPHIBEX and Marine final exercise (MARFINEX).

“From language barriers to differences in tactical planning, preparing for the exercise presented challenges, but by the time we concluded training with the Royal Thai and Republic of Korea Marines, most of these differences seemed to fall away and we found it much easier to work together effectively,” said Sgt. Dody Martinell, the headquarters company platoon sergeant for LAR.

Hat Yao beach-a vast stretching coastline in the shadow of a shark fin-shaped mountain-was the location for the AMPHIBEX, where the U.S., Thailand, the Republic of Korea, and Singapore armed forces worked together to simulate the assault of a beachhead. MRF-SEA’s medical team played a key role during planning and evacuation rehearsals, providing critical medical expertise while performing casualty evacuation drills alongside the Royal Thai Navy and U.S. Army.

Led by U.S. Navy Lt. Gricel Rodriguez, the MRF-SEA medical team coordinated resources to strengthen partner nations’ higher echelons of care. The goal was to conduct a mass casualty drill, incorporating multiple scenarios that required both U.S. and Thai-specific procedures for tactical combat casualty care and patient movements. Working alongside the U.S. Army’s 745th Forward Resuscitative and Surgical Detachment, the teams successfully executed a patient movement drill using full expeditionary resuscitation equipment.

Overcoming the language barrier was a significant challenge, but it was an inspiring experience for the MRF-SEA team as a whole. Rodriguez explained, “Interoperability is always the key to readiness. In case of conflict, we will need each other’s resources. By learning each other’s processes now, we’ll be in the best position to succeed when it matters most. The Royal Thai forces were highly engaged and receptive to our guidance. We learned some new techniques from them as much as they did from us.”

As the exercise neared its conclusion, Marines from LAR and MRF-SEA gathered at Ban Chan Krem for the MARFINEX, a series of training events including counter-unmanned aerial systems flights, sniper engagements, mortar and artillery coordination, and a mechanized assault. Within the notional training scenario, the multilateral force of U.S., Thai, and Korean Marines had moved inland following their amphibious assault of an enemy beachhead. As the scenario developed, allied forces identified an enemy defensive position by utilizing sUAS to conduct aerial reconnaissance. The MARFINEX brought the training scenario to a conclusion, as the enemy’s defensive position was overwhelmed and destroyed by the combined force. Throughout the training, Marines from each country learned how to work with one another and achieve a common mission as allies.

While the Marines and Sailors of MRF-SEA executed training on the ground, the actions from the air elements of the exercise ensured the synchronized delivery of assets to make it all happen. To transport personnel, cargo, and ammunition to Thailand for MARFINEX, the MRF-SEA air coordination cell worked closely with Marine Aerial Refueler Transport Squadron 152 from Iwakuni, Japan, and VMGR-153 from Marine Corps Air Station Kaneohe Bay, Hawaii. This coordination ensured that necessary resources were transported efficiently and on time.

U.S. Marine Corps Capt. Heather Hamilton, assistant air officer with MRF-SEA, underscored the critical role of communication in the success of MARFINEX.

“We coordinated airspace for small UAS and managed fire direction requests from the [fires and effects] coordinator,” Hamilton said. “For MARFINEX, I worked directly with the Thai aviators in Korat’s Joint Live Fly Cell to create airspace for small UAS operations. The relationships we build with the Royal Thai Air Force will be invaluable for us.”

The exercise not only strengthened the technical proficiency and readiness of all participating forces but also solidified lasting relationships built on the knowledge that interoperability between allies and partners is a necessity for stability in the Indo-Pacific. As the nations continue to work together, Cobra Gold remains a key platform for ensuring regional security and preparedness for future challenges.