The credibility of the U.S. extended nuclear deterrence is a critical issue that goes beyond the question of Japanese psychology and perception. It potentially influences the direction of Japan’s security policy, compellence and/or attacks by adversaries on Japan, and even Asian stability.
Japan’s faith in the extended U.S. nuclear deterrence was shaken even before the Trump era. Since the end of the Cold War, China has steadily modernized and built up its nuclear forces, and the survivability and penetrability of its strategic nuclear forces targeting the United States has improved.
In the 2010s, North Korea bolstered nonstrategic nuclear forces targeting Japan and moved toward the acquisition of strategic nuclear forces that kept the U.S. within range. These developments not only heightened Japan’s threat perception of China and North Korea but also made Japan increasingly concerned about a possible decoupling between Japan and the U.S.: “Will the U.S. defend Japan even if its mainland is exposed to danger?”
In addition, the downsizing of U.S. nuclear forces under the Obama administration caused Japanese conservative politicians and security officials to be skeptical of the appropriateness of the U.S. deterrence posture. In particular, the retirement of the TLAM-N, a nonstrategic nuclear-tipped cruise missile whose variants can be launched from a variety of platforms, including submarines, increased concerns about the decoupling between Japan and the U.S. because it could result in a situation where the U.S. deterrence posture in Asia depends solely on strategic nuclear forces and could create a gap in the U.S. escalation ladder.
Moreover, the victory of Donald Trump, who bluntly criticized the Japan-U.S. alliance for its inequality and provided verbal approval of Japan’s nuclear armament during the U.S. presidential election campaign in 2016, triggered a general skepticism that the U.S. would be reluctant to engage in Japanese security.
Immediately after his inauguration, Trump issued a reassuring statement following a summit with Prime Minister Shinzo Abe: “The U.S. commitment to defend Japan through the full range of U.S. military capabilities, both nuclear and conventional, is unwavering.” In response to North Korea’s launch of ballistic missiles the following day, he added publicly, “The United States of America stands behind Japan, its great ally, 100 percent.” The resolve shown by the new and mercurial U.S. president on extended nuclear deterrence offered Japan a sense of security.
More important to Japan was the fact that the Trump administration reinforced the U.S. commitment by building up its nuclear forces. Stating that “the United States will enhance the flexibility and range of its tailored deterrence options for its and allied security,” the Nuclear Posture Review (NPR) in February 2018 announced the development of nonstrategic nuclear forces — a low-yield sea-launched ballistic missile (SLBM) warhead and a new submarine-launched cruise missile (SLCM). The NPR featured these as alternatives to TLAM-N, which had contributed to the deterrence extended to U.S. allies in Asia.
This measure was exactly what Japanese conservative politicians and security officials had sought in order to close the gap in the U.S. escalation ladder. For this reason, the Abe administration praised the NPR as demonstrated by the foreign minister’s comment that it clarified “the U.S. resolve to ensure the effectiveness of its deterrence and its commitment to providing extended deterrence to its allies including Japan.”
To be sure, the U.S. building up its nonstrategic nuclear forces creates the strategic issue of lowering the nuclear threshold and political issues over the introduction of nuclear weapons on allies’ soil. But in the current Asian security environment, it also increases the credibility of U.S. extended deterrence.
At the same time, however, the Trump administration has been heightening Japan’s concerns about U.S. credibility. Trump’s dramatic shift in policy toward North Korea has had a particularly large impact. In a sudden decision in March 2018, he elected to meet with North Korean leader Kim Jong Un. The Trump-Kim summit in June brought an end to the strict complete, verifiable, irreversible denuclearization (CVID) expression that had hitherto been used to describe U.S. demands vis-a-vis Pyongyang’s nuclear weapons program.
When North Korea launched a number of short-range missiles this summer, the Trump administration repeatedly stated that it did not see that as a problem.
On the surface, the Japanese government has acknowledged the U.S. shift in North Korean policy. But the change could leave Japan feeling somewhat skeptical about Washington’s will to provide extended nuclear deterrence. The Abe administration had been applying maximum pressure on North Korea in collaboration with the Trump administration, with a focus on CVID. But the U.S. changed its policy without prior consultation, effectively leaving Japan behind. For Tokyo this only served to reconfirm Trump’s unpredictability and it is increasingly worried that he may make a “deal” with North Korea that ignores Japanese security.
More specifically, Tokyo is concerned about the possibility of agreements on freezing strategic nuclear forces that reach the U.S., allowing Pyongyang to maintain nonstrategic nuclear forces that do not reach the U.S. but keep Japan within range.
The Trump administration’s acceptance of North Korea firing short-range missiles shows that this concern is hardly misplaced. If the U.S. were to reach such an agreement, Japan will conclude that Washington has sacrificed the security of an ally for the sake of its own interests. This would decisively increase Japan’s feelings of distrust in the U.S. as a provider of extended nuclear deterrence.
In general, the credibility of extended deterrence depends on the intentions and capabilities of the state offering it. As the U.S. president’s repeated contradictions of earlier remarks and his broken promises, including his abrupt North Korea policy shift, have increased the uncertainty of U.S. intentions, the credibility of U.S. extended nuclear deterrence has become more dependent on its nuclear capabilities.
In these circumstances, if U.S. nuclear forces are not to be strengthened as planned in the NPR, the U.S. commitments to defend Japan and other allies can be seen as empty promises and bluffs. American diplomacy will doubtless be quite unstable in the run-up to the presidential election in 2020, but it will also be important to take careful note of U.S. military trends.
Shingo Yoshida is an associate professor at the Department of Law, Kindai University