Part 1: In Defense of Conventional Punishment: Why Japan’s Defensive Realism Requires Offensive Capability
By Will Kielm
October 17, 2024
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After nearly eight decades spent maintaining a strict self-defense posture since World War Two, Japan made a pivotal shift in its grand strategy in December 2022. The government introduced a landmark National Security Strategy which made a significant political commitment to acquiring long-range “counterstrike capabilities”, which are traditionally viewed as “offensive capabilities”. Despite its historical commitment to the senshu boei (exclusively self-defense) principle, Japan has incrementally reinterpreted Article 9 of its constitution to broaden the concept of self-defense over the years. Most recently it took steps to acquire previously out-of-bounds counterstrike capabilities, driven largely by China’s military modernization and North Korea’s escalating nuclear provocations.
Although the People’s Republic of China (PRC) and North Korea have often labeled these developments as aggressive, the characterization is predictably one-sided. Both China and North Korea have developed offensive capabilities of their own while touting their ostensible defensive purposes. However, in the Indo-Pacific offensive and defensive capabilities are generally indistinguishable. Japan must recognize that purely defensive technologies are insufficient to ensure its own security and uphold the rules-based regional order. To credibly deter revisionist powers armed with offensive capabilities, Japan must move beyond the flawed mindset that draws a sharp distinction between offensive defense and defensive defense and strategically shift towards the acquisition of counterstrike capabilities that can impose significant costs on potential aggressors.
The Debate on Perception and the Offense-Defense Distinction
Understanding Japan’s definition of “self-defense” and examining its shift from defense to offense evokes two of the most fundamental conceptual questions in international relations: 1) can a state enhance its military capabilities with purely defensive intentions without being perceived as the aggressor? and 2) to what extent can states reliably distinguish between offensive and defensive capabilities? The first question touches upon what political scientists refer to as the “security dilemma”, a concept John Herz described in 1950 as a situation where the pursuit of security leads states to accumulate power, increasing the insecurity of others. This “dilemma” triggers a vicious cycle of power competition, where no state can ever feel entirely secure. Scholars have long contended that, despite a state’s non-aggressive intentions driven solely by security concerns, its military buildup may still be perceived as aggressive by others. In its pursuit of greater security, a state may ultimately be seen as driven not only by defense but also by “greed”—such as economic gain, prestige, historical claims, domestic pressures, or ideology.
The late political scientist Robert Jervis in 1976 cited Germany’s naval expansion under Kaiser Wilhelm II in the late nineteenth and early twentieth centuries as one historical example of the security dilemma. Although Germany claimed its fleet buildup was intended for defensive purposes and to protect its growing overseas empire, London perceived Berlin’s actions as a direct challenge to British naval supremacy, contributing to rising tensions between the two countries and the eventual outbreak of World War One. Similarly, when the Soviet Union deployed missiles in Cuba during the Cuban Missile Crisis of 1962, Moscow framed the move as a defensive measure to deter future U.S. aggression. Nevertheless, the United States perceived Moscow’s decision as highly offensive, heightening tensions to the brink of nuclear war.
Some scholars, however, argue that states can strengthen their militaries without being misperceived as aggressors. By focusing entirely on defensive capabilities during a military buildup, states can credibly signal that their motives are driven by security concerns alone, thereby achieving what is known as a defense-dominant posture within the “offense-defense balance”. This approach provides credible reassurances to potential adversaries that their actions are driven by security concerns rather than aggressive intent. As George Quester once famously argued, “Defensive developments in military practice will be more welcome than offensive ones, simply because they make war less likely among such states.” These scholars are known as “defensive realists” and emphasize the importance of maintaining a balance of power (or a balance of “threats“) that favors defense to avoid an escalatory spiral between great powers.
Numerous defensive realists have argued that defensive weapons are distinguishable from offensive ones and that states can enhance their security without threatening others. Charles Glaser and Chaim Kaufmann offer an objective measurement of the offense-defense balance: states can treat the balance as the ratio of the cost of the forces the attacker requires to take territory to the cost of the forces the defender has deployed. Only by acknowledging this offense-defense distinction and focusing exclusively on defensive as opposed to offensive military technologies can states avoid the so-called “cult of the offensive”—as Stephen Van Evera warned—and thereby prevent a careless escalation spiral that could lead to a costly war.
This line of optimistic, defensive realist analyses that draw an artificial distinction between offensive and defensive capabilities has been contested in the political science literature. For instance, Keir Lieber in 2005 empirically demonstrated that the variance between offensive and defensive advantages is very rarely significant and that variables other than military technologies—namely the distribution of power and difference in military doctrine and strategy—are far more likely to determine military outcomes. Even John Mearsheimer, one of the leading proponents of foreign policy restraint among academics, acknowledged the difficulty of distinguishing defensive and offensive capabilities, which forces states to aggressively and indiscriminately pursue military power to cause security for themselves.
Such indistinguishability between offensive and defensive capabilities nullifies the security dilemma, leaving Japan with a straightforward path. Instead of managing escalation through defensive technologies, Japan must focus on achieving deterrence and escalation dominance, which necessitates the embrace of acquiring counterstrike capabilities.
Will Kielm is a Research Fellow at the Edwin O. Reischauer Center for East Asian Studies at the Johns Hopkins School of Advanced International Studies (SAIS). He recently graduated from the University of Michigan’s Gerald R. Ford School of Public Policy.