Across the US joint force’s global footprint, terms like “interoperability” and “build interior lines” are commonly heard. In Army service component commands and geographic combatant commands, these terms burst forth as clarion calls, concise expressions of what US forces must achieve in their areas of responsibility. After a tactical-level unit completes a task, commanders often state that they’ve built interior lines and developed interoperability with partnered nation X. Yet, in many cases, there is no metric by which to measure progress or success. Interoperability is not an end-state, but rather a means to an end. Operations that aim to improve interoperability should not do so with that as their final objective; they must also assist us in understanding posture requirements and, subsequently, help set priorities for infrastructure investments.

Too often, the US military—across all services—participate in combined (nation-to-nation) exercises with our partners, yet fail to extract the maximum value. The cycle is familiar: we conduct the exercise, exchange high-fives, swap patches, and depart. We do not maintain enduring relationships. The communication network built for each event is temporary, often leaving the partner nation without access to key information afterward. This often makes US presence a requirement for success in the exercise. We aren’t meeting our partners where they are, asking what they need, or working collaboratively to build lasting interoperability or interior lines. An annual exercise simply doesn’t achieve lasting impact. In many countries, there must be more continuous investment between exercises that helps inform our posture initiatives and prioritize infrastructure development.

The Problem

Component commands aren’t adequately staffed to maintain ongoing and on-the-ground relationships during most of what the joint force broadly categorizes as OAIs—operations, activities, and investments. The US military tends to interact with leadership from partner nations, but operational-level understanding of their militaries is limited. In most cases, units conducting OAIs are neither permanently stationed in these countries nor focused exclusively on one region. Tactical-level engagements lack the seniority needed to create programs or glide paths that build on prior investments, leading to a gap in understanding of partner capabilities at the operational level. This gap often leads to a lack of clarity across the US services on what to prioritize for joint infrastructure investments. How, then, can the US joint force build interior lines, with limited resources outside of major exercise windows, while expanding operational-level interoperability? The answer is by sharing more information.

A Potential Solution

In April 2023, the 1st Multi-Domain Task Force (1st MDTF) participated in Balikatan 2023 and found itself in a position to address this challenge. 1st MDTF was tasked with establishing a bilateral coordination center between two joint task forces: the United States’ I Marine Expeditionary Force (I MEF) and the Republic of the Philippines’ Northern Luzon Command (NOLCOM). In typical US/ally exercise constructs, two common mistakes emerge: (1) we (US forces) focus solely on exercise-related intelligence, and (2) we overclassify all products for the exercise and place them on a temporary network nearly inaccessible to most partners. 1st MDTF took a different approach, opting to share real-world, unclassified information about NOLCOM’s area of operations using a sensitive but unclassified (SBU) network. The coordination center was dubbed the Combined Information and Effects Fusion Cell (CIEFC). During the CIEFC’s initial operation, Major General Jay Bargeron was the commanding general of 3rd Marine Division. While conducting a tour of the CIEFC, Bargeron, who is now the J5 for US Indo-Pacific Command, stated “This is how we transition to a joint exercise model.”

After the exercise, the CIEFC concept of real-world data sharing led to an invitation from the Armed Forces of the Philippines for 1st MDTF to continue an enduring, on-the-ground partnership with NOLCOM. This marked a significant step toward understanding capabilities of a major ally, and arguably greatly enhanced placement and access for the unit—in other words, building interior lines. At Land Forces Pacific Conference 2023, General Charles Flynn, commander of US Army Pacific, referenced the 1st MDTF CIEFC as a prime example of his concept of the Pacific’s strategic landpower network.

1st MDTF has been operating forward in the Philippines for more than twenty consecutive months—greatly contributing toward joint force understanding of the theater in a true competition environment. While 1st MDTF continues to operate and grow the CIEFC in the Philippines, the concept has also expanded into an exercise in Malaysia hosted by 3rd MDTF. Lieutenant General James Jarrard, the former deputy commander of US Army Pacific, discussed the CIEFC concept during an interview in Malaysia. He noted that bringing in new technologies to training events can help share multidomain awareness with our partners.

At its core, the CIEFC concept is a method to partner with an operational-level headquarters that assists the appropriate commander to understand threats in the operational environment. This concept is valuable even with countries the United States does not have a formal intelligence-sharing agreement with. As Flynn noted, Philippines commanders “can actually see into the maritime and air littorals,” informing decisions by the country’s leaders.

Leveraging Unclassified Information, Not Intelligence

The power of open-source tools, commercial imagery, social media, and SBU networks cannot be overstated. These tools foster operational awareness without compromising information managed by the US intelligence community, thereby enabling the sharing of near-real-time data with partner nations. By democratizing access to critical unclassified information, barriers thought to be imposed by classification guides become more permissive. This allows allies and partners to develop a shared understanding of the operational environment. Commercial satellite imagery, for instance, provides high-resolution data on terrain, movement, and infrastructure, empowering partners to make more informed decisions. Social media scraping tools also allow information about emerging incidents to be gathered and, more generally, foster an understanding of the information environment.

During Balikatan 2023, 1st MDTF’s choice to share real-world, unclassified data with NOLCOM resulted in deeper cooperation and a higher level of commitment. This approach empowered NOLCOM to operate with greater autonomy while still benefiting from US support. The SBU network became a vital conduit for continuous, safe information exchange beyond the exercise itself. The success of this approach underscores how unclassified tools can enhance situational awareness while maintaining operational security.

SeaVision: The Starting Point for Maritime Domain Awareness

SeaVision, a US Department of Transportation–sponsored maritime domain awareness tool, adds another layer of unclassified situational awareness. This web-based platform allows partners to track maritime vessels, analyze shipping patterns, and potentially detect irregular or illegal activity at sea. By integrating SeaVision into joint exercises and ongoing operations, US forces and their allies can develop a comprehensive maritime picture, enhancing the ability to monitor key areas and respond to emerging threats. SeaVision and similar platforms are routinely used by a range of US units and organizations in the joint force.

SeaVision’s capability to provide real-time insights into maritime traffic directly supports both US and partner operations. When applied in exercises like Balikatan, SeaVision extends the benefits of shared situational awareness beyond the exercise itself, enabling partners to manage their maritime domains proactively. Integrating SeaVision into routine operations strengthens partners’ independent operational capacities while contributing to joint mission objectives. With sponsorship from the United States, allies and partners can get access to SeaVision. And with minimal planning, additional layers of visualization can be added that normally only US service member accounts can display.

SeaVision gives our allies and partners a valuable understanding of vessels that are emitting publicly available electronic signatures as required by the International Convention for the Safety of Life at Sea. Those electronic signatures are referred to as automatic ship identification systems (AIS). SeaVision also gives our partners and allies the ability to assess how vessels are maneuvering in exclusive economic zones that might indicate the presence of suspicious activity. Large vessels maneuvering in irregular patterns could indicate illicit activity. A lack of electronic signatures is also telling as a vessels unwillingness to use its transponders may signal nefarious intent.

Flight Trackers: A Starting Point for Air Domain Awareness

Many allied and partnered nations use their equivalents of the United States Federal Aviation Administration to observe and manage airspace. Some militaries do not have radar capabilities or the ability to monitor airspace. If the military is not integrated with its country’s airspace management organization, it can lead to disjointed airspace awareness. An effective platform for monitoring airspace is a visualization tool that displays transponder data.

Websites like FlightAware and others that display transponder data provide a critical starting point for understanding what occurs in a nation’s airspace. Illicit and suspicious activity can be monitored by finding anomalies in routine information. Deviations in well-established patterns in the sea or air could indicate illicit activity.

Looking Forward: Lessons for the Joint Force

Building relationships is critical to expanding interior lines. Assisting our allies and partners in gaining access to information is a simple solution to building interest in what the United States can provide. This can be the mechanism to build interoperability. Tools like SBU networks and SeaVision enable US and partner forces to maintain situational awareness and continue refining coordination outside formal training environments.

This continuous sharing of information allows partner nations to develop a common operational picture, contributing to strategic depth. Interior lines are not just about supporting and reinforcing forces efficiently in a crisis but also about sustaining the network built during exercises for long-term readiness. Ongoing engagement, even remotely, ensures that partners remain prepared and that relationships and infrastructure essential to combined operations remain strong. To replicate the success of 1st MDTF’s model, joint force units can consider five principles:

  1. Focus on real-world scenarios. Exercises should integrate real-world information to ensure joint activities are immediately applicable to current operational challenges. This ensures that both US and partner forces develop skills and capabilities they can use in real scenarios, not just theoretical ones. For units that regularly participate in these exercises, consider between-exercise engagements that can contribute toward furthering interoperability and building infrastructure.
  2. Sustain engagement beyond exercises. Building interior lines and interoperability requires consistent investment. Units should develop mechanisms to maintain communication and information sharing between major exercises to prevent stagnation in relationships and operational capability.
  3. Tailor solutions to partner needs. Joint force units must actively engage with partners to understand their specific needs and objectives. Instead of relying on a one-size-fits-all approach, US forces should codevelop solutions that reflect each partner’s unique operational environment.
  4. Use sensitive but unclassified networks. By leveraging SBU networks and unclassified tools like commercial imagery and SeaVision, units can share relevant information continuously without the restrictions of classified systems. This encourages broader participation, fosters operational transparency, and allows partner or allied forces to take lessons learned back to their units. Most importantly, our partners and allies need access to the information we develop during exercises. Often, when we depart exercises, we take most of the learned information with us.
  5. Record and maintain interoperability metrics. Army Regulation 34-1, Interoperability is the only manual in the joint force that codifies four levels of interoperability (0–3), and the capabilities that joint forces and their partners need to achieve to be rated at each level. For example, a partner country without an intelligence-sharing agreement with the United States will never achieve level 3, and almost certainly won’t achieve level 2. Additionally, a digitally linked a common operational picture is rated as a level 3 capability. RAND noted in 2024 that a key to building interoperability is to continually assess, monitor, and evaluate metrics while integrating critical activities and strategic objectives.

Challenges to Implementation

Change, of course, can be difficult. If an effective new idea were easy, there’s a good chance we would already be doing it. In the case of the recommendations described above, two challenges stand out. The first is foreign disclosure. Sharing military intelligence or combat information in developed or mature theaters of operation can be considered routine. There are systems and processes in place for a foreign disclosure officer or representative to interpret applicable security classification guides (SCGs) for lawful disclosure of classified military information including military intelligence. In countries without an intelligence-sharing agreement with the United States, or specificity in the theater SCG, units must rely on theater-level approval to share information—and intelligence. The distinction is important. Information does not have analysis behind it, but intelligence does. A geospatial-intelligence specialist providing an unclassified commercial satellite image is information. A geospatial-intelligence specialist providing a satellite image with annotations and assessments is intelligence. This concept can become murky in practice, but a unit foreign disclosure officer can assist in navigating complexity of relevant policies.

The second challenge is finding the right partner unit and venue. Several militaries around the world are restructuring and acquiring new technologies to increase global or regional competitiveness. However, many militaries lack joint doctrine or have not rehearsed joint structure. This can lead to a lack of understanding of why an army would be interested in the maritime domain or why a navy would be interested in the land domain. Finding the right unit to assist in the concept hinges on finding the correct organization in a military to partner with. Consistently, an exercise concept that pairs a US service component with a partner service component limits our ability to exercise above the tactical level. Units must find the right partner unit and exercise to demonstrate value. In short, the joint force needs to expand beyond army-to-army or navy-to-navy exercises.

The success of building interior lines and achieving true interoperability hinges on sustained collaboration beyond major exercises. Through unclassified networks, tools like SeaVision, and real-world data, the US military can establish continuous situational awareness and enhance the operational capabilities of its partners. The approach adopted by the 1st MDTF during Balikatan 2023 demonstrates that strategic use of unclassified data not only empowers partner nations but also builds long-term relationships, trust, and coordination. 3rd MDTF is also expanding upon this capability to other countries in the Pacific. These engagements go beyond tactical-level training engagements. As William Nance noted in Modern War Institute, “By our own doctrine, we should be focusing more across our partners entire defense capacity, not just its tactical formations.”

To replicate and expand on this success, joint force units must focus on maintaining engagement between exercises, tailoring solutions to partner needs, and grounding collaboration in real-world scenarios. This ongoing commitment to interoperability will strengthen the collective ability to respond effectively in contested environments, fortifying both infrastructure and strategic alliances for future challenges.

Nathan D. Levy is a US Army major with United States Army Pacific’s 1st Multi-Domain Task Force. He is a veteran of several campaigns in Iraq and Afghanistan and has operational experience in Egypt, South Korea, Japan, Germany, Senegal, and the Philippines.

The views expressed are those of the author and do not reflect the official position of the United States Military Academy, Department of the Army, or Department of Defense.

Image credit: Nathan D. Levy