The United States Considers Reinforcing Its ‘Pacific Sanctuary’

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Could Japan see an increase in the presence of U.S. military capabilities and personnel in the years ahead? It’s looking possible. Soon after he took office, Secretary of Defense Lloyd Austin ordered a posture review to ensure that the U.S. global footprint is the right size to support U.S. strategy. The results of the review will inform the Biden administration how best to allocate military forces in pursuit of U.S. interests.

As part of the review, the United States will consult with its treaty allies and consider its alliance commitments. In the Indo-Pacific, the U.S. presence is concentrated in Japan, with about 56,000 active military personnel and all four services represented. Despite agreements between the United States and Japan years ago that have led to a gradual reduction in the U.S. presence in Japan, such as the number of U.S. Marines in Okinawa, Japan’s continued importance to U.S. strategy and Tokyo’s increased willingness to be more proactive in the security domain mean that Japan could see an uptick in U.S. military presence — more ships, more troops, even long-range strike missiles — after this review is complete.



The current U.S. force presence in Japan, including its capabilities and disposition, is a product of history and U.S. vital interests. Immediately after World War II, U.S. occupying forces used many of the same bases and airfields that Imperial Japanese forces had used. Then, guided by the logic inherent in NSC-68 — the historic presidential directive issued in 1950 that called for a military buildup to compete with the Soviet Union — the U.S. presence grew after the end of the American occupation of Japan in 1952. The exigencies of the Korean War also shaped the U.S. presence in Japan. Although the Korean conflict was confined to the peninsula, because North Korea (and, by extension, China) had no power-projection capabilities beyond their immediate shores, Japan was a sanctuary for the United States. As such, Japan and Okinawa (which, unlike the rest of Japan, remained under U.S. occupation until 1972) served as a power-projection platform for U.S. operations and a sustainment and logistics hub. Both served a similar role in the Vietnam War.

Collectively, unchallenged U.S. air and sea control in the region became the foundation for U.S. regional presence. This enabled the United States to project force when, where, and how it wished from its secure bases in Japan. While the shape of the U.S. presence in Japan has changed over time, its contribution to U.S. and allied interests has been reaffirmed by every administration from President Harry S. Truman through President Joe Biden.

Sanctuary No More

Japan is no longer the sanctuary for U.S. forces that it once was, and this has been true for several decades. First and foremost, all U.S. (and Japanese) bases are well within range of adversaries’ air, sea, and missile platforms. China, for example, has invested heavily in missile and rocket forces to achieve sea control over the East and South China Seas from an arsenal spread throughout its vast continental hinterland. North Korea, too, has developed significant missile capabilities. The fact that weapons today are much more accurate at distance further sharpens the challenge. For example, China’s development of a variant of its DF-21 missile, dubbed a “carrier killer,” threatens to keep the U.S. Navy at a considerable distance from any potential operation. Finally, emerging technologies provide U.S. adversaries with ubiquitous, pervasive, detailed, and accurate surveillance of all of Japan, thereby improving their ability to strike with greater accuracy and lethality. For example, more sophisticated satellites will provide near continuous coverage of the Japanese archipelago and the waters around it, hypersonic weapons with evasive trajectories will make defending against them more difficult, and AI combined with autonomy will provide faster decision-making and greater domain awareness, thereby disadvantaging militaries that rely solely on the speed of humans. Gone are the days of the United States being able to surreptitiously move forces to and within the region without an adversary taking note or holding the forces at risk. Taken together, these developments mean that U.S. force posture in the Western Pacific, long a strong bulwark of U.S. conventional deterrence, has become increasingly vulnerable.

The United States understands this. China projects power on almost a daily basis in campaigns designed to intimidate Taiwan, Japan, and other nations. China’s forces are routinely present in the air and seas surrounding Japan and Taiwan, presumably to test opposing forces’ reactions and possibly coerce a response. In addition to other reasons, Washington’s continuing attention to protecting U.S. vital interests, fulfilling its alliance commitments, and protecting the territory and lives of U.S. allies and partners has meant that the United States has not simply pulled back from its overseas presence and let other countries fend for themselves.

What Could Change?

Being within range of adversary weapons does not sound the end of U.S. forward presence, particularly given the global range of some types of weapons. Nor can U.S. allies change their geography. If U.S. withdrawal is not an option, and long-range precision weapons have made every U.S. base in Japan a target, there are several areas that potentially could see change after the Department of Defense’s posture review.

One area could be air and missile defenses. Commandant of the U.S. Marine Corps Gen. David Berger recently commented that it is imperative to think anew about overseas installations, acknowledging that U.S. forward bases and infrastructure are vulnerable to adversaries. In the Indo-Pacific, for example, Chinese ballistic missiles pose a considerable threat to U.S. air bases. A 2015 RAND report examined the effect of ballistic missile salvos targeted at Kadena Air Force Base in Okinawa and found that a large salvo could close the runway for days or even weeks. Because abandoning U.S. forward bases is not realistic, Berger suggests that more efforts are needed to raise the costs of launching an attack on these bases, to reduce operational dependence on them, and to improve their resilience across dimensions and domains. With such a heavy U.S. presence in Japan, the United States may look to pursue improvements in both passive and active defense measures. Some would be invisible to the general public, such as the hardening of critical infrastructure like munitions and fuel depots or airplane shelters. Others would be more visible, such as dispersing and distributing forces across greater areas. Spreading out U.S. capabilities as well as fuel, apron space, runways, and prepositioned munitions would require physical space, which would likely mean increasing the U.S. footprint in Japan. Similarly, if the United States seeks to improve active defense capabilities in Japan, perhaps by installing more American-operated Patriot systems or Terminal High Altitude Area Defense batteries, this too could necessitate a greater U.S. presence.

Related to improved defensive measures is a second possible change: offensive long-range ground fires. Adm. Phil Davidson, head of U.S. Indo-Pacific Command, recently outlined his requests to Congress for the Pacific Deterrence Initiative, which included calls for ground-based, long-range fires. These precision-strike fires, meant to support air and maritime maneuver at great distances, would help to hold Chinese assets at risk, including those at sea, in the air, and at considerable distance from the coast on the Chinese mainland. Ever since the United States withdrew from the Intermediate-range Nuclear Forces Treaty in 2019, there have been persistent rumors of the United States wanting to secure bases in the Pacific for missiles with ranges formally prohibited by that treaty, anywhere between 500 to 5,500 km. In August 2019, then-Secretary of Defense Mark Esper said he was in favor of placing such missiles in the region relatively soon. With the threat posed by China not going away, it would not be surprising if, as part of the posture review, the United States approaches Japan with requests to host these types of strike capabilities. This is particularly appealing not just because of Japan’s geography, but because of Japan’s own incremental movements toward achieving stand-off missile capabilities. If the United States and Japan are concerned about trying to offset the threat posed by China, including eliminating the missile gap they currently face with China, then fielding long-range ground fires in robust numbers would make sense as one possible option.

In addition to strengthening base defenses and an offensive strike element, a third possible change could be the United States seeking to increase its “sealift” capabilities — ships that can carry soldiers, weapons, or supplies. Berger’s vision for the U.S. Marine Corps a decade hence, Force Design 2030, proposes new operational concepts to protect U.S interests from a widely distributed, mobile, operationally resilient network throughout the First Island Chain. Maneuvering agile, mobile, compact forces, such as squads and platoons, throughout the littoral among islands calls for small, speedy, agile ships. Specifically needed are relatively small ships with enough square footage for vehicles mounting long-range weapons to support sea and air control, and troop capacity of around 40 people. In Japan, this could mean the need for finding homeports for more of these types of ships.

Surface combatants, carrier strike groups, and established amphibious group forces may also need reinforcement. When we consider that China’s three maritime forces — the People’s Liberation Army Navy, the China Coast Guard, and the People’s Armed Forces Maritime Militia — outnumber the forces that the United States and Japan can bring to bear against them, the demand for naval forces in an emergency or conflict will likely far exceed the supply of what the U.S. Navy, U.S. Marine Corps, and Japan’s Maritime Self-Defense Force could provide. The United States and Japan have not been growing their fleets at the same pace as China, meaning that they will likely have fewer available ships than China in the future. Fewer ships mean reduced ability to deliver force by sea. Should the United States want to try to reverse this, it may choose to move naval combatants currently based in Guam, Hawaii, and California to Japan. Back in 2015, the Center for Strategic and Budgetary Assessments found that basing an additional aircraft carrier at Yokosuka would meet the entire demand for carrier coverage in the Pacific without having to build more ships to fulfill the U.S. Navy’s regional commitments. If the same logic holds true, it is possible that the United States may seek a second carrier strike group to be homeported in Japan. Or, understanding that a carrier strike group may be impractical due to space concerns, a second option could be another amphibious ready group. One is already homeported at Sasebo. Deploying a second would enable one group to stay in port and one to be deployed, thereby permitting nearly continuous deployed amphibious capability without demanding any large space requirement.

A fifth possible posture change could come in the form of a joint warfighting U.S. command element in Japan. Since the Korean War, the United States has maintained a combined headquarters in the Combined Forces Command that allows a U.S. commander in Seoul to maintain a posture prepared to fight at a moment’s notice should North Korea resume hostilities, which the Army refers to as a “fight tonight” posture. The United States has nothing close to that in Japan, even though Japan is home to the largest number of U.S. regional forces. China’s force projection capability puts Japan in a similar “fight tonight” situation where hostilities could break out at a moment’s notice, which could demand similar structure and readiness to that in place on the Korean peninsula. Instead, the individual service components report directly back to their service boss in Hawaii and, in a contingency, the U.S. Indo-Pacific Commander would exercise operational command. Maintaining the type of command and control necessary in an environment where U.S. equipment and personnel have difficulty communicating with one another, as well as with the commanders overseeing an operation, would challenge any type of U.S. operation run out of Hawaii. And in peacetime, as long as command and control resides at the Indo-Pacific headquarters in Hawaii it will be difficult to foster the type of daily interaction and training that is needed in Japan to build a coherent combined response. Given that China has moved to unify its forces, there is always the possibility that the United States may seek to counter this with a U.S. joint command element in Japan to drive joint and combined contingency plan development and planning for a combined fight.

There are other possible options not reviewed here that the force posture review may also recommend. One is increasing the size of U.S. Forces Japan through an increase in permanent staff to perform the duties of an operational command element. Another is the periodic reinforcement of either the U.S. Seventh Fleet or III Marine Expeditionary Force with certain skills and expertise to create a joint command element from the nucleus of a service command element. Yet another would be increasing the U.S. Army contribution through the addition of a Multi-Domain Task Force including air and missile defense forces.

None of these changes would be easy or cost-free for the United States or for Japan. It is also possible that they could elicit local Japanese opposition. While there are many cases of local communities accepting an expanded U.S. or Japanese presence, such as Yamaguchi prefecture’s support of the expansion of Marine Corps Air Station Iwakuni or Okinawa’s acceptance of the expansion of the Air Self-Defense Force base in Naha, there are also examples of local opposition to new or relocated U.S. presence. The most well-known example is the ongoing effort to relocate the Marine Corps Air Station Futenma from its current location in southern Okinawa to a new location in northeast Okinawa. While objections to changing the footprint of the U.S. presence in Japan will differ depending on the community, one can imagine possible reasons ranging from noise concerns, environmental issues, and opposition to plans for greater pier space or expanded fencelines that infringe upon existing fishing grounds or agricultural lands. And if Japan’s cancellation of Aegis Ashore last summer teaches us anything, it is that one can never rule out the possibility that the public may oppose the introduction of something new out of fear of safety issues it might pose to the local community.

The possibility of local opposition suggests that the development and implementation of any force structure recommendations should be an all-of-government effort in both nations. Through close and continuous consultation, the allies could better position themselves to show their publics and relevant government agencies the purpose of the proposed force posture changes to enhance their shared security. Close consultation may also lead the Japanese government to consider valuable force structure changes on their part, thereby further enhancing overall alliance effectiveness. Such an alliance effort is much more powerful than just the sum of its parts.

While it is still unknown what results the posture review will bring, the recent 2+2 meeting in Tokyo demonstrated that the alliance is stronger than ever given the common positions shown on China and the need to find ways to bolster the alliance. That strength, combined with an increased proactiveness by Japan, means that it is possible that Japan could see an uptick in U.S. military presence after this review is complete. One thing is clear. If the words of the late Sen. Mike Mansfield were true in the past, that the “U.S.-Japan relationship was the cornerstone of stability in the Far East and in the world, bar none,” the regional challenges that the alliance faces now may make that sentiment even truer today.



Lt. Gen. (ret.) Wallace C. Gregson, Jr. is a former commander of III Marine Expeditionary Force in Japan, and former assistant secretary of defense for Asian and Pacific security affairs.

Jeffrey W. Hornung is a political scientist at the nonprofit, nonpartisan RAND Corporation. 

Image: Sgt. Maj. Michael Cato