U.S. Marines in Iron Fist 2025: Strengthening Pacific Partnerships Through Bilateral Amphibious Operations

The 2025 iteration of Exercise Iron Fist represents a significant milestone in U.S.-Japan military cooperation, with American Marines and Japanese forces conducting their largest bilateral amphibious training exercise in Japan’s strategically vital southwest islands region.

Running from February 19 through March 7, 2025, this exercise showcased the evolving partnership between the two nations amid growing regional security challenges.

At the heart of Iron Fist 2025 stands the 31st Marine Expeditionary Unit (MEU), serving as the primary American force in the exercise.

The 31st MEU holds a unique position as the Marine Corps’ only permanently forward-deployed MEU, maintaining a continuous presence in the Indo-Pacific region.

Based at Camp Hansen on Okinawa, this force of approximately 2,200 Marines and sailors serves as America’s premier crisis response capability in one of the world’s most strategically important regions³.

The 31st MEU’s current ground combat element centers on Battalion Landing Team 2/4 (BLT 2/4), built around the 2nd Battalion, 4th Marines. This reinforced infantry battalion brings substantial amphibious assault capabilities to the exercise, supported by Combat Logistics Battalion 31, which provides essential sustainment and logistics operations.

The integration of these elements creates a complete Marine Air-Ground Task Force capable of rapid deployment and sustained operations across the diverse terrain of Japan’s southwest islands.

A notable component of the Marine participation involved aviation assets from Marine Aircraft Group 36 (MAG-36), based at Marine Corps Air Station Futenma on Okinawa. Four MV-22B Osprey tiltrotor aircraft from MAG-36 relocated to Camp Ainoura on Kyushu for the duration of the exercise. This movement represented part of a broader 2016 U.S.-Japan agreement designed to reduce training activities around Okinawa while maintaining operational readiness.

MAG-36’s participation underscored the critical role of aviation in modern amphibious operations.

The unit, which forms part of the 1st Marine Aircraft Wing and III Marine Expeditionary Force, specializes in providing assault support aircraft for Marine Air-Ground Task Force operations.

The Osprey’s unique capabilities — combining the vertical lift of a helicopter with the speed and range of a fixed-wing aircraft — make it particularly valuable for operations across the scattered islands of Japan’s southwest region.

Iron Fist 2025 emphasized practical, realistic training scenarios designed to enhance interoperability between American and Japanese forces. The exercise focused specifically on amphibious operations while working to improve the working relationship between U.S. and Japanese ground forces. Training activities spaned multiple domains, including advanced marksmanship, amphibious reconnaissance, fire and maneuver assaults, bilateral logistics coordination, medical support operations, and comprehensive fire support including mortars, artillery, and close-air support.

Recent training events have demonstrated the exercise’s hands-on approach to building partnership capabilities. Marines from BLT 2/4 have conducted live-fire exercises alongside soldiers from Japan’s 1st Amphibious Rapid Deployment Regiment. These bilateral marksmanship sessions enable forces from both nations to improve their lethality and readiness while learning from each other’s techniques and procedures.

Logistics cooperation represents another crucial element of the training. U.S. Marines from Combat Logistics Battalion 31 have worked directly with Japanese Ground Self-Defense Force personnel on helicopter support team operations, including complex external lift procedures.

In a significant milestone, American Marines successfully conducted the first-ever external lift of a Japanese tactical vehicle, demonstrating growing interoperability in logistics support operations.

The shift of Iron Fist from its traditional California location to Japan’s southwest islands reflects the changing strategic environment in the Indo-Pacific region. Until 2023, the exercise was conducted at Marine Corps Base Camp Pendleton in California before moving to its current location in response to regional security concerns.

Japan’s southwest islands have become increasingly important due to China’s territorial claims on the disputed Senkaku Islands and Beijing’s focus on conducting military exercises simulating a blockade of Taiwan. Chinese military forces, including People’s Liberation Army Navy ships and aircraft, routinely transit through international waters and airspace around Japan’s southwest region, highlighting the strategic significance of this area.

The exercise locations themselves tell the story of this strategic focus. Training areas include multiple sites across the region: Camp Hansen and Kin Blue Beach Training Area on Okinawa, Camp Ainoura in Sasebo and Camp Takayubaru in Kumamoto on Kyushu, and the southwest island of Okinoerabu. This geographic spread allows forces to train across the diverse terrain types they might encounter in real-world operations while demonstrating allied commitment to regional security.

The exercise benefited from significant naval support, with multiple U.S. Navy vessels providing the maritime foundation for amphibious operations. The amphibious assault ship USS America (LHA-6) served as the primary platform, supported by the amphibious dock landing ship USS Rushmore (LSD-47) and amphibious transport dock USS San Diego (LPD-22). This naval component provided the Marines with realistic ship-to-shore movement capabilities essential for amphibious operations.

The Japan Maritime Self-Defense Force contributed its own vessels, including the tank landing ship JS Kunisaki (LST-4003) and minesweepers JS Awaji (MSO-304) and JS Chichijima (MSC-605). This combined fleet provided a comprehensive maritime training environment that mirrors the complex, multi-national nature of potential real-world operations in the region.

Beyond its immediate training value, Iron Fist 2025 serves as a cornerstone of the broader U.S.-Japan security relationship. The exercise, now in its 19th iteration, has evolved from its origins as a California-based training event to become a symbol of alliance cooperation in the face of regional challenges. The annual nature of the exercise allows both forces to build institutional knowledge and develop lasting professional relationships that extend far beyond the formal training period.

The participation of Japan’s Amphibious Rapid Deployment Brigade (ARDB), 1st Helicopter Brigade, and units from the Western Army alongside their American counterparts demonstrates Japan’s commitment to developing its own amphibious capabilities.

This parallel development of capabilities on both sides strengthens the overall alliance while ensuring that both nations can contribute meaningfully to regional security.

Iron Fist 2025 represented more than a training exercise — it serves as a demonstration of allied resolve and capability in one of the world’s most strategically contested regions. The Marines of the 31st MEU, working alongside their Japanese counterparts, are developing the skills, relationships, and interoperability necessary to respond to future challenges in the Indo-Pacific.

As regional tensions continue to evolve, exercises like Iron Fist become increasingly important for maintaining the delicate balance of power that has ensured stability in the region for decades.

The professional relationships built during these training events, the tactical and operational lessons learned, and the demonstrated commitment to partnership serve as powerful deterrents to potential aggression while reassuring allies and partners throughout the region.

The success of Iron Fist 2025 will likely influence future iterations of the exercise and similar bilateral training events.

As both nations continue to adapt their forces to meet emerging challenges, the lessons learned from this exercise will inform military planning, force structure decisions, and alliance coordination for the evolving “fight tonight” force.

Sources:

DVIDS notes associated with the photos used in this article.

https://news.usni.org/2025/01/24/u-s-marines-japanese-forces-to-drill-in-southwestern-japan-in-iron-fist-exercise

https://www.stripes.com/theaters/asia_pacific/2025-01-27/amphibious-okinawa-japan-china-16620493.html

https://www.iiimef.marines.mil/Media-Room/News/Article/Article/4071402/iron-fist-25-strengthening-us-marine-and-japan-forces-combined-amphibious-capab/

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