Following the effective withdrawal of Japan’s Aegis Ashore deployment plan, former Ambassador to the United States Ryozo Kato examines the limits of Japan’s independent deterrence, the Japan–U.S. alliance, military threats from North Korea, China, and Russia, possible alternatives involving cruise missiles and enhanced submarine capabilities, and the need for an advanced “defensive strike capability.”

July 17, 2020
The deployment plan for the land-based Aegis Ashore missile interception system has effectively been withdrawn.
Japan stands apart from the rest of the world in that its security and national defense policies are not merely “non-offensive,” but at times may even be described as “pacifistic.”
I find myself impressed that the country has managed to sustain this posture until today, amid the COVID-19 crisis.
【The “Bottle Cap” Theory That Spread After the War】
After the war, the idea known as the “bottle cap” theory remained influential in the United States, including among senior military officers.
According to this analogy, Japan was like a genie confined within Aladdin’s lamp, and once the lid was removed, it would again bring disaster upon the world.
For that reason, there was a deeply rooted view that Japan should be permitted to achieve economic growth, but that any expansion of its military power should be restrained at an appropriate level.
Behind this attitude was America’s confidence and pride that it could control not only Japan but also the Far East and the western Pacific.
I believe that this perception has not entirely disappeared even today.
Because the United States held this view, Japan was able to enjoy the benefits of a division of labor under which it could say, in effect, “Let America take care of the difficult and weighty matters, while we behave as an exceptionally good child and fully enjoy the economic benefits.”
For a long period, the United States also tolerated this arrangement, ultimately regarding it as serving its own interests.
The situation appears to have changed considerably since then.
Looking back, until the end of the Cold War, was not American military power consistently superior to that of the Soviet Union, regardless of the image presented to the outside world?
The Soviet side may well have displayed both bravado and anxiety.
Similarly, my intuitive belief is that the military power of the United States still far exceeds the widely publicized military power of China.
Even so, however, in the event of a conflict, the United States could never achieve “fifteen victories in fifteen battles” or pitch a “perfect game.”
Our side would certainly suffer substantial damage as well.
At that point, the United States would undoubtedly make a selection between what must be protected and what must be abandoned, based on the order of priority of the national interests it must defend.
The term “triage” is sometimes used, and the concept has certain similarities.
【Japan Must Hold a High Priority for Protection】
I have long believed that it is essential for Japan to hold a high priority among the interests that the United States would protect at such a time.
For that reason, I believe that Japan must build and maintain a Japan–U.S. alliance under which an armed attack against Japan is immediately recognized by the United States as an attack against itself.
Japan’s deterrence as a whole consists of the combined strength of Japan’s independent deterrence and the deterrence possessed by the United States under the Japan–U.S. Security Treaty.
However, because of the structure of Japan’s domestic laws and basic national policies, Japan’s own deterrent power is subject to severe limitations.
The defense budget is placed under strict constraints in a parliamentary democracy, and a substantial increase cannot be expected.
Japan therefore has no choice but to seek the most effective possible use of the resources available to it.
Generally speaking, deterrence is not fundamentally “offensive.”
It is a defensive concept intended to make an adversary with hostile intent refrain from attacking Japan.
Within that framework, Japan must naturally consider the adversary’s ① military capabilities, ② intentions, and ③ patterns of behavior.
When Japan objectively considers the threats that its deterrence must address, the danger posed by North Korean missiles has tended to be emphasized in recent years, partly because it is comparatively easy to obtain public understanding of that threat.
However, no theory of deterrence can be adequate if it fails to consider not only China’s large number of missiles, but also its expanding land, air, and naval forces, cyber capabilities, artificial intelligence, and electronic warfare capabilities.
Russia’s military power must also be considered.
Deterrence should not encourage an adversary’s hostile intentions.
To put it plainly, it should be efficient and directed at the “pressure point” the adversary most dislikes having touched.
From this perspective, I have no means of knowing the cost-effectiveness of Aegis Ashore, including how much deterrent value it would have against China.
The first of the stratagems in the ancient Chinese work The Thirty-Six Stratagems is “Deceive the Heavens to Cross the Sea.”
It apparently means repeatedly showing the enemy the same action until it becomes familiar, thereby inducing complacency, and then launching a sudden attack.
This brings to mind China’s conduct in the South China Sea, the East China Sea, and the waters surrounding the Senkaku Islands.
【Improving Deterrence Through an Alternative Policy】
If the outcome is merely that “Japan has completely abandoned Aegis Ashore,” it will only be welcomed by forces seeking to weaken the Japan–U.S. alliance.
However, if that decision is accompanied by an alternative policy, such as the deployment by Japan or the United States of more cost-effective sea-launched or ground-launched cruise missiles, or a fundamental enhancement of Japan’s submarine capabilities, then Japan’s overall deterrence may instead be substantially strengthened.
North Korea’s missiles are a major source of concern.
These include not only nuclear weapons but also numerous medium-range missiles, such as the Nodong, capable of reaching Japan.
Nevertheless, a nation’s deterrence must be more comprehensive.
In addressing the continuing threats of both military and political intimidation, Japan should continue to exercise strict self-restraint regarding an “offensive strike capability.”
At the same time, there appears to be no reason for Japan to hesitate in advancing toward the strengthening of an advanced “defensive strike capability.”
【Editorial Note】
The central issue raised by this article is not a simplistic choice between possessing striking power and possessing none at all.
Deterrence is not a capability designed to begin a war.
It is a capability intended to persuade an adversary not to launch an attack.
It does not necessarily follow that interception alone is sufficient.
The ability to make an adversary anticipate consequences it cannot accept if it attacks may also form part of deterrence.
The expression “defensive strike capability,” as used by Ryozo Kato, should be understood in this sense.
There are also limits to depending entirely on the overwhelming military power of the United States for Japan’s security.
Even if the United States maintains its great military strength, a crisis will inevitably require it to establish priorities according to its own national interests.
The argument that Japan must build and maintain an alliance in which an attack on Japan is recognized as an attack on the United States goes to the heart of the Japan–U.S. alliance.
At the same time, Japan’s independent deterrent capabilities are restricted by its legal framework, basic policies, and defense budget.
Precisely because these constraints exist, Japan must determine how its limited resources can be allocated most effectively to alter an adversary’s calculations.
If the withdrawal of Aegis Ashore is not followed by anything else, a gap may be created in Japan’s deterrence.
If it is accompanied by a clear alternative policy, including more cost-effective equipment and stronger submarine capabilities, it may instead be possible to enhance deterrence as a whole.
What Japan requires is neither unlimited military expansion nor a policy of unarmed idealism that turns away from reality.
Japan must strictly restrain offensive power while calmly and concretely constructing an advanced defensive strike capability capable of protecting its people and territory.