A C2 Structure for a Strong U.S.-Japan Alliance

This commentary is part of the Exploring New Horizons: Japan’s Defense Priorities project, a CSIS Japan Chair initiative featuring analysis by leading Japanese and American scholars examining the implications of Japan’s new national security and defense strategies and opportunities for bilateral cooperation.

The U.S. Department of Defense, with the support of both Congress and the U.S. defense industrial base, has built the most capable military force in the world. The United States has unmatched power projection capability, the ability to establish air and maritime dominance far from its shores and conduct brigade-level amphibious operations, and the resources to execute large-scale ground maneuver operations. But despite all of this, the United States will not be ready to deter and defeat its most capable adversary—China—in the demanding technological environment it faces in the next five years.

To address this problem, the United States should again turn to one of its greatest strengths: its allies and partners. Most crucial of these is Japan, whose 70-year partnership with the United States continues to evolve and strengthen year over year. The next logical step, and one that will have a disproportionate effect in deterring Chinese aggression, is the development of a more integrated and efficient command and control (C2) structure between the two allies.

The China Challenge

The United States relies heavily on large-scale military mobility and sustainment capacity, trained and empowered non-commissioned officers, the use of precision-guided munitions at range, and expansive intelligence collection and analysis capabilities to deter and, if needed, defeat adversaries. But today’s adversaries, particularly China, are investing in similar weapons and sensor systems, and they are using emerging technologies in an attempt to neutralize the United States’ operational superiority and reduce the ability of U.S. forces to rapidly detect, track, and eliminate an adversary.

China has achieved meteoric growth in terms of its military capability and capacity. The Chinese Communist Party (CCP) was embarrassed by the relative impotence of China’s military during the Third Taiwan Strait Crisis, in 1995–1996, when two U.S. carrier strike groups operated with impunity in the waters immediately off China’s coast. The CCP has spent the past 25 years addressing that problem—building a military force designed specifically to place U.S. air and maritime operations at risk within the First Island Chain, and soon within the Second Island Chain as well. China’s investments in advanced technologies have targeted observed U.S. weaknesses, such as the missile defense of ships and airfields, looking to create asymmetric advantages for its forces. China has also spent aggressively on technology that would marginalize existing U.S. advantages, such as military mobility and precision targeting. While the United States labeled China as the “pacing threat,” China has acted to develop and procure weapons as if the United States was actually their pacing threat. Not surprisingly, China’s actions have outperformed U.S. rhetoric.

Whether the conflict is about the East China Sea or Taiwan, it is likely that China’s war plans will include a comprehensive pressure campaign that uses malicious cyber activity and other information warfare tools to achieve the following objectives: (1) blind U.S., Japanese, and Taiwanese intelligence networks and silence each ally’s ability to communicate with forward forces; (2) weaken allied critical infrastructure, both to paralyze military mobility and logistics enterprises and bring allied economies to a standstill; and (3) use disinformation campaigns to freeze national security decisionmaking. The purpose of these actions would be to deliver a strong signal to U.S. leaders about the vulnerabilities in U.S. and allied systems, ensuring that the United States does not come to the support of its allies and partners.

This challenge posed by emerging technology is complicated by a number of other operational issues. The first is geography. The United States is trying to deter conflict in Taiwan and in the East or South China Seas, areas within 100 miles of Chinese ports and airfields but 8,000 miles from the U.S. West Coast. Second, China is also likely to have a first-mover advantage—as an authoritarian regime with rapacious designs, they are much more likely to strike the first blow in a conflict. Finally, China maintains a strong advantage in the gray zone, able to conduct operations that push the bounds of international law, lack transparency, and slowly, sometimes imperceptibly, establish advantage. While the United States cannot fix these problems directly, it needs to address their impact.

Japan would face these same challenges in an East China Sea crisis emanating from the Senkaku Islands. While Japan is much closer than the United States to potential conflict zones, China’s investments in air and naval power, malicious cyber activity, and use of aggressive gray zone tactics pose significant operational challenges even for the increasingly capable Japan Self-Defense Forces (JSDF). 

Despite these challenges, the United States and Japan can overcome China’s asymmetric advancements, maintain the United States’ ability to project power and impose costs, and together ensure the security and stability of the region. This effort will require targeted investments in multiple areas, but the area that promises the most immediate, long-lasting, and consequential advantage is building a more effective and integrated C2 structure between the region’s most capable allies: the United States and Japan.

Operational Integration

The positive impact of operational force integration is not just a theory. Multiple iterations of a wargame addressing a Taiwan conflict scenario showed that the introduction of integrated Japanese forces consistently reduced allied casualties by nearly 30 percent. Similar wargaming for an East China Sea scenario would likely demonstrate an even more beneficial reduction in Japanese casualty rates if an integrated U.S. force were to support a counter-Senkaku Islands campaign. This is not an academic exercise for either country—if the United States and Japan can field a well-integrated force, they are more likely to win and more likely to win well.

To best understand what an integrated force looks like, it is useful to understand the “stages” or attributes of combined military C2 enterprises. Partner militaries can work together at four different levels of cooperation: deconflicted, coordinated, integrated, or unified. Higher levels of cooperation are a product of shared equipment and networks, organizational structures, experience levels, and, most importantly, frequency of training, exercising, and operating together.

  • Deconflicted: The lowest level of cooperation is deconflicted, which means each military does its utmost to stay clear of the other’s forces, with a premium placed on not operating in the same battle space. This is best represented by the idea of “you go to the left, I will go to the right, and you should not under any circumstances go to the right.”
  • Coordinated: The next level is coordinated, where an effort is made to time movements together. In other words, “you go left at 1100 and I will go right at 1115, hoping that the adversary has focused on your move.”
  • Integrated: The third level of operational employment is integrated. It is the idea of mutually supporting forces. This can be expressed as “you go left at 1100, and I will come in behind you at 1115, amplifying and enhancing the effect of your forces.” This is the level at which U.S. and NATO forces have been operating for decades.
  • Unified: Finally, forces can be considered unified when they operate seamlessly together and can transition C2 between national elements with ease. In this scenario, “we will both go left at 1100 under my command, maximizing the value of each of our capabilities.”

The highest level of combined enterprises drives efficiencies, minimizes shortfalls, and enhances performance. One can think of this force coordination in mathematical terms: a deconflicted force is at best “2 + 2 = 3,” while an integrated force might be “2 + 2 = 5.” 

Ongoing Efforts

U.S. and Japanese military forces, led in this effort by their respective navies, have worked hard over the past 50 years to move from a deconflicted partnership in the 1970s to well-coordinated forces by the 2010s and are beginning to demonstrate aspects of an integrated force. The advances of the past 50 years reflect a growing employment of similar weapons systems, improved communications, and a comprehensive bilateral training and exercise program.

Similar weapons systems are extremely helpful, since they lead to shared capabilities, shared tactics, and shared operational concepts and they support shared communications. The United States and Japan have a number of important systems in common. In the naval space, the Japan Maritime Self-Defense Force (JMSDF) is centered around Aegis-equipped destroyers, Standard Missiles, Seahawk helicopters, P-3 aircraft, and carrier-based F-35 aircraft. The Japan Air Self-Defense Force (JASDF) uses F-35 and F-15 fighters, along with E-2C and E-2D Advanced Hawkeye early-warning aircraft. The Japan Ground Self-Defense Force (JGSDF) uses the M-270 Multiple Launch Rocket System (MLRS), Guided Multiple Launch Rocket System (GMLRS), M110 Self-Propelled Howitzer, Patriot Missile air defense system, and Apache and Cobra helicopters. All indigenously produced Japanese systems are built to interoperate with these U.S.-supplied systems, so the total force is highly interoperable with U.S. forces. No two countries on earth have such a large quantity of highly interoperable equipment.

The shared weapons systems have also allowed for integrated communication and data-sharing networks. This includes traditional data links, such as Link 16, and situational awareness tools, such as the Combined Enterprise Regional Information Exchange System – Japan (CENTRIXS-J). Even more valuable is the shared use of the Cooperative Engagement Capability (CEC), a data link that shares fire-quality tracking data. The JMSDF has CEC in their latest Aegis destroyers, as does the JASDF in their latest E-2D aircraft. The CEC system is a force-enhancement tool that achieved the goals of Joint All-Domain Command and Control (JADC2) before the U.S. military even conceived of the JADC2 concept.

Organizational attributes also contribute to force integration, and the JMSDF, JASDF, and JGSDF have carefully developed their operational structures to reflect, and work with, the U.S. forces that are forward stationed in Japan.

Probably the most important element of operational integration is a comprehensive bilateral training and exercise program. Among the Japanese services, the JMSDF has best mastered this effort, with nearly 30 years of weekly training events and comprehensive annual exercises, known as AnnualEx. These are routinely the most comprehensive exercises the U.S. Navy conducts with any ally or partner. Similarly, the JGSDF and JASDF have been significantly increasing routine training events and exercises with their U.S. partner forces over the past 10 and 20 years, respectively. In addition, annual U.S.-Japanese joint exercises—Keen Edge (a command post exercise) and Keen Sword (a field training exercise)—have expanded to be among the most complex, multi-domain events that U.S. forces participate in.

Command and Control: The Final Step

Weapons systems, organizational structures, networks, and exercising are all critical elements of operational collaboration, but both Japan and the United States recognize that there is one additional clear requirement: building an effective C2 mechanism to support bilateral operations. Currently, two very dissimilar organizations provide C2 for bilateral operations. The United States uses the Indo-Pacific Command (INDOPACOM), a large, unified combatant command situated in Hawaii and responsible for everything from “Hollywood to Bollywood to the Arctic and Antarctic.” Japan uses the Joint Staff Office, a largely administrative staff, to coordinate the efforts of its three services. Neither is an agile, solely operationally focused organization, constantly preparing for, and suitably located to respond to, an attack by a well-equipped authoritarian adversary with a first-mover advantage. Instead, both the United States and Japan need to establish dedicated standing joint force headquarters to include bilateral operational centers, and other related mechanisms.

Japan has moved to rectify the situation first, committing to establish a Permanent Joint Headquarters (PJHQ) over the next two years. Once established, this would provide a dedicated commander who would take charge of Japan’s joint operations. The PJHQ commander would monitor and assess readiness for all services for current operations, ranging from a Taiwan crisis to North Korean missile launches to Senkaku Islands defense missions. The PJHQ commander would collaborate with both U.S. military commands forward stationed in the Western Pacific and INDOPACOM. Having a Japanese operational commander as a counterpart to U.S. commanders is expected to enable closer communications and more effective operations on a daily basis as well as during a crisis response.

The Japanese PJHQ commander will have a number of steady-state roles: formulating Japan-specific joint defense planning; developing bilateral plans with INDOPACOM; managing Japanese Major Commands across all three services; and planning and executing joint and bilateral exercises. The PJHQ would also play a leadership role in commanding Japanese forces in the conduct of full-spectrum operations, both nationally and bilaterally.

The United States is also developing a new construct for operational command in the Western Pacific. The fiscal year 2023 National Defense Authorization Act (NDAA) directed the secretary of defense to establish a Joint Force Headquarters (JFHQ) in the Indo-Pacific theater of operations to serve as an operational command to integrate “joint all domain command and control effects chains and mission command and control, including in conflicts that arise with minimal warning.”

At present, the senior U.S. joint command in Japan is U.S. Forces Japan (USFJ), located at Yokota Air Base in Tokyo. The USFJ commander has limited responsibilities, including administrative negotiations with the Japanese government and the JSDF and coordinating implementation of the status of forces agreement governing U.S. forces in the country. The operational control of U.S. forces in Japan is held by INDOPACOM. While the USFJ commander is also the commander of the U.S. 5th Air Force; the other service commands in Japan, U.S. Seventh Fleet (Navy), the 3rd Marine Division, and U.S. Army Japan, have no operational ties to the USFJ, and the USFJ is not resourced or equipped to execute joint operational command, if the operational ties did exist.

As the secretary of defense determines how to address the NDAA guidance and develop an appropriate JFHQ for INDOPACOM, a few key questions will need to be addressed: How persistent will the command’s operational control of forces be? What will be its responsibilities for developing operational plans? What will be the JFHQ’s responsibilities for operational integration with critical allies and partners such as Japan, Australia, the Philippines, and Taiwan? And what will be its location, with Guam, Japan, Hawaii, and at-sea as options?

The JFHQ would benefit from a persistent existence, as that would allow for constant interactions with Japan’s PJHQ, the Australian Joint Operational Center, and the Philippine and Taiwan armed forces. The JFHQ could coordinate and, when appropriate, lead training and exercise events with regional allies and partners. This effort would also include building and assessing national, bilateral, and multilateral war-planning efforts. This should include wargaming at the military level and supporting wargaming at the political-military level. 

While it may appear that locating the JFHQ in Japan would be most beneficial to U.S.-Japanese cooperation, that may not be accurate. By locating in Japan, the JFHQ might be hamstrung in responding to actions away from Japan. Rather, it would increase the agility of the JFHQ, and even the PJHQ, by placing the JFHQ outside of Japan.

As Japan develops its PJHQ and the United States develops its JFHQ, there is a great opportunity to lock in a strong operational support system that contributes significantly to U.S. and Japanese forces consistently operating at an “integrated” level. The one country that will be most closely watching U.S.-Japanese efforts is China, and if the two allies do this correctly, they can significantly contribute to deterring future conflict in the East China Sea or Taiwan.

Mark Montgomery is a retired rear admiral with the U.S. Navy and senior director of the Center on Cyber and Technology Innovation at the Foundation for the Defense of Democracies.

This project is made possible with support from the Government of Japan.

Mark Montgomery

Senior Director, the Center on Cyber and Technology Innovation, the Foundation for the Defense of Democracies