ROK-US Combined Division

How Fighting Together Enables 2nd Infantry Division

By LTC Brennan Speakes, LTC Jared Ferguson, MAJ Ian Murdoch, MAJ Seohyun Park, MAJ Bradley Rager and MAJ Wesley Mooseman

Article published on: May 20, 2025 in the Armor Spring 2025 Edition

Read Time: < 10 mins

The U.S. Army’s Mission Command Training Program “supports the collective training of Army units as directed by the Chief of Staff of the Army” through the execution of its Warfighter Exercise (WFX) scenario. ¹ As the premier training event for division and above formations, the WFX provides opportunities to stress and train units across the six warfighting functions. However, the 2nd Infantry Division must contend with another challenge in its operational environment that the Mission Command Training Program does not replicate but the nature of the Korean Theater of Operations (KTO) demands.

The Indianhead Division is the only combined division in the U.S. Army since it has members of the Republic of Korea (ROK) Army serving and working directly with their U.S. counterparts. Moreover, the U.S. and Korean armies appropriately refer to the division as the 2nd Infantry Division/ROK-U.S. Combined Division (2ID/RUCD). The combined nature of 2ID/RUCD enabled the division to successfully execute WFX 24-2 by creating mutual understanding between the two armies, ensuring a unity of purpose and action throughout operations. This enhanced the division’s ability to:

• Conduct timely intelligence operations.
• Execute a responsive, combined targeting process
• Prioritize protected assets obligatory to division wet gap crossing operations
• Conduct a forward passage of lines with a foreign military under enemy contact

2ID/RUCD’s combined staff coordinates actions in post-Korean War armistice conditions and is well-rehearsed in working together to achieve operational objectives. During the WFX, the combined staff’s unique nature was vital to the division’s success. ROK Army operations, logistics, signal, protection, intelligence officers, and non-commissioned officers (NCOs) enabled 2ID/RUCD to make decisions rapidly. While exploring options for adjusting the battlefield framework, the division staff was able to coordinate simultaneously with both the ROK Army and U.S. Army headquarters to develop coordination measures and synchronize actions immediately. The staff’s integration surpassed traditional habitual relationships and united the team’s purpose in meeting the commander’s intent. 2ID/RUCD demonstrated a substantial unity of purpose and effort within the intelligence warfighting function.

Intelligence operations

Intelligence operations in a combined staff are highly challenging, given the different security requirements and national caveats when working with foreign militaries. Throughout WFX 24-2, the combined intelligence section (C-2) capitalized on those differences. It used the strengths of both nations, most notably in intelligence support to targeting, situational awareness, and support to the rapid decision-making synchronization process (RDSP).

The intelligence warfighting function within the U.S. Army forces decision-point tactics, while the ROK Army is more detail-oriented. Within intelligence support to targeting, this resulted in the balance of providing the commander with the relevant analysis required to target capabilities while providing a high level of detail. This ultimately contributed to an effective targeting process that removed threat capabilities from the battlefield. The U.S. Army’s emphasis on decision-point tactics and the ROK Army’s detailed analysis enabled the commander to understand how the high-payoff target list shaped the enemy, allowing resources to be focused effectively.

Analysts process massive amounts of data within the U.S. intelligence enterprise through the various sensors and reporting mechanisms. During large-scale combat operations, vast data and information can be challenging to synthesize into a suitable format for the commander’s situational awareness. The ROK Army has the reverse problem and needs help generating enough reporting to create a solid picture. Once again, the two intelligence backgrounds created a situation that complimented the strength of both sides. U.S. forces were able to collect the necessary data, while ROK intelligence officers rapidly processed that data and created a format easily interpreted by the commander for situational awareness.

Finally, through RDSP, intelligence Soldiers from both armies worked closely to generate products useful at all echelons of command rapidly. The ROK Army doctrinally works on a compressed timeline, and the U.S. Army is naturally flexible. Therefore, combining these approaches led to detailed planning products with minimal turnaround time, allowing the combined staff to publish detailed orders rapidly. The successful intelligence analysis enabled an in-depth targeting process and delivered lethal fires.

Lethal fires success

Applying lethal fires through fire control systems was one of 2ID/RUCD’s most successful characteristics during WFX 24-2. The 2ID/RUCD is well-postured to conduct combined fires based on technical and organizational factors. ROK Army Fires officers and liaison officers (LNOs) from adjacent units on the Division staff provided organizational benefits to Fires planning and execution. For example, while conducting a forward passage of lines (FPOL) of the 2nd ROK Corps, the staff and LNOs were able to leverage 2nd Corps firing units early in the FPOL by establishing them in their position area artillery within 2ID/RUCD’s area of operations. LNOs and ROK Army fires officers also leveraged adjacent unit fires assets into the Division Air-Tasking Order, facilitating the FPOL and enabling higher headquarters’ mission. The uniquely combined nature of the 2ID/RUCD staff and the ability to work closely with allied units at short notice and throughout the year has ensured 2ID/RUCD is capable of rapid, well-coordinated combined fires in any potential conflict. The firing units were critical to ensuring we had protection through the operational environment, and 2ID/RUCD leveraged them to support our protection.

Limited protection assets across the KTO dictated the refinement of the Protection Prioritized List to protect specific assets for specific durations. For instance, the multi-role bridging company bridges were critical for the division’s wet-gap crossing. The division engineer cell’s ROK officer was crucial to conducting the rapid analysis of where to cross these gaps. He used both U.S. and ROK Army geospatial assets to identify the critical bridges along with the requisite data, including the bridge length, seasonal river width, and probable water velocity, to facilitate the requirements to support the gap crossing sites. The data collected helped identify the necessary protection assets and key terrain required for the operation. His knowledge of the capabilities of the ROK Army formations was invaluable in preparing and conducting the FPOL with the 2nd ROK Corps, which was able to preposition critical air-defense assets. Without these assets, enemy forces would have been able to target and disrupt the FPOL’s momentum and disrupt 2ID/RUCD operations.

The forward passage of units during combat is challenging enough between U.S. units. Its complex nature and detailed planning require a common understanding at the lowest level possible. This challenge is made more difficult during combined operations. A common understanding of roles, responsibilities, and control measures is paramount to maintaining tempo and mitigating risks. 2ID/RUCD effectively conducted an FPOL by quickly understanding the problem and developing a solution utilizing the relationships across the combined staff.

During WFX 24-2, 2ID/RUCD planned and executed an FPOL between its organic forces and the 2nd ROK Corps in a time-constrained environment under enemy contact. The combined nature of this FPOL required a detailed understanding of each headquarters’ disposition and operations. The division further identified issues from the difference between the U.S. and ROK Armies’ doctrinal approaches to the passage of lines. Likewise, 2ID/RUCD’s passing of a more extensive, non-U.S. higher headquarters created uncertainty in command and support relationships. The nature of 2ID/RUCD’s combined staff allowed it to rapidly integrate headquarters’ operations due to its standing relationships with the adjacent ROK units.

Early integration

2ID/RUCD leveraged its combined U.S.-ROK staff by integrating the 2nd ROK Corps early in the planning process. 2ID/RUCD planners previously developed an FPOL operational framework and concept as a sequel plan, which enabled the division to leverage previous work to establish a common understanding. The 2nd ROK Corps provided its planned scheme of maneuver, enabling 2ID/RUCD to adjust its graphic control and fire support coordination measures to facilitate 2nd ROK Corps’ future operations. This common framework enabled discussions on roles, responsibilities, and command relationships between each headquarters.

Similarly, 2ID/RUCD was able to organize its command posts to support the FPOL effectively, leading to greater situational awareness and understanding across both headquarters. Therefore, 2ID/RUCD was able to tailor its schemes of support across the warfighting functions to enable the passage of lines. Planners were able to bridge the concepts between U.S. and ROK doctrine to develop acceptable and feasible schemes and relationships. 2ID/RUCD’s scheme of collection and fires was essential to shape the 2nd ROK Corps’ follow-on operations. 2ID/RUCD and 2nd ROK Corps identified and agreed on triggers using doctrinal considerations for the transition of command and support relationships between 2ID/RUCD and 2nd ROK Corps. These were critical in supporting the passage of lines and allowing both formations to maintain momentum throughout the operation.

Conclusion

2023 marked seven decades since the end of combat operations in the Korean War. More importantly, however, it marks 70 years of a ROK/U.S. alliance that remains strong today. The Korean phrase, “katchi kapshida,” or “we go together,” captures that alliance’s strength. The relevant and robust term exemplifies today’s U.S./ROK relationship and served as an edict for 2ID/RUCD’s WFX.

The combined nature of 2ID/RUCD enabled the division to successfully execute WFX 24-2 by creating mutual understanding between the two militaries and ensuring a unity of purpose and action throughout operations. This enhanced the division’s ability to conduct combined large-scale combat operations. As a ROK planner on the 2ID/RUCD staff described it: although we wear different uniforms, the two staffs have developed an understanding and respect for one another, allowing our armies to overcome tactical and doctrinal differences and build trust as teammates. This respect further solidifies the U.S./ROK alliance.