U.S. Defense Secretary James Mattis and his South Korean counterpart Han Min-Koo at the national cemetery in Seoul, South Korea, February 2017.
U.S. Defense Secretary James Mattis and his South Korean counterpart Han Min-Koo at the national cemetery in Seoul, South Korea, February 2017. 
Oh Dae-il / News1 / REUTERS

Last week, James Mattis made his first international trip as U.S. defense secretary. Over four days in Japan and South Korea, Mattis sought to reassure officials in both countries of Washington’s commitments to them. Many in East Asia are worried about the direction of U.S. foreign policy under the new administration of President Donald Trump, who during his campaign chastised Japan and South Korea for not paying enough for U.S. military support and even suggested that Tokyo and Seoul should consider developing nuclear weapons—signs, it seemed, that the superpower on which Japan and South Korea have long depended was considering abandoning them.

Like Trump’s November meeting with Japanese Prime Minister Shinzo Abe and Trump’s phone calls with South Korean officials, Mattis’ visit suggested that the new administration is attempting to walk back the effects of some of Trump’s earlier rhetoric. The timing of Mattis’ visit was critical, coming as it did amid growing criticism from regional observers that the Trump administration was set to cast aside the United States’ pivot to Asia and focus more on threats from the Middle East. But perhaps more important was Mattis’ tone: The defense secretary did not press allies on burden-sharing but sought instead to reassure and listen to them. That was the right move. Washington will need its East Asian allies in the coming months, as tensions will undoubtedly resurface around the region’s many flashpoints, such as the Korean peninsula and the East China and South China seas. Later this week, Abe and Trump will meet in Washington and Florida. Like Mattis, Trump should use those meetings to reassure Abe of Washington’s commitment to its alliance with Japan.


Japan’s concerns about Trump’s vision for the United States’ strategy in Asia are twofold. On the security front, Tokyo has been alarmed by Trump’s claims that Japan has enjoyed the benefits of Washington’s alliance commitment without providing much in return. “You know we have a treaty with Japan where if Japan is attacked, we have to use the full force and might of the United States,” Trump mused in August, during his campaign. “If we’re attacked, Japan doesn’t have to do anything. They can sit home and watch Sony television.”

Those remarks may have set off more surprise than anger in Japan. That is mostly because the U.S.-Japanese alliance has matured over the past few years as Japan has worked to improve its own defense capacity: Japanese officials have hardly been idle. Since his election in late 2012, Abe has sought to reform Japan’s antiquated security and defense architecture, which was developed in the aftermath of World War II under U.S. occupation. His government has created a National Security Council, developed Japan’s first National Security Strategy, and pushed through a host of security reforms that took effect last year, increasing the flexibility and permitted uses of Japan’s Self-Defense Forces. Tokyo has implemented many of those changes under a revised set of bilateral defense guidelines, finalized in 2015, that seek to tighten Japan’s security partnership with the United States. 

U.S. Navy and Japan Maritime Self-Defense Force ships during an exercise south of Japan, November 2014. 
Mass Communication Specialist 3rd Class Chris Cavagnaro / U.S. Navy / Reuters

During a meeting with Abe, Mattis reaffirmed the United States’ commitment to Tokyo as “100 percent,” stressing that Washington was not wavering on its security pledges. Perhaps more critical, Mattis assured Japanese officials that the United States still considers the Senkaku Islands (known as the Diaoyu Islands in China, which also claims them) as covered by Article 5 of the U.S.-Japan Security Treaty, meaning that the United States would come to Japan’s aid if the islands were attacked. The islands have been the focal point of tensions between China and Japan for several years. Despite U.S. assurances, China continues to sail fishing, commercial, and Coast Guard vessels around the territories in an effort to assert its claim over them.

Mattis’ visit may have allayed some of Japan’s security concerns. But Japanese policymakers are still worried about Trump’s positions on global trade. By withdrawing the United States from the Trans-Pacific Partnership, or TPP, Trump has upended a major plank of Abe’s plans to revitalize the Japanese economy. Abenomics, as the prime minister’s economic program is known, depends on a combination of fiscal stimulus, monetary easing, and structural reforms. The TPP would have advanced the last of those efforts by helping to modernize Japan’s economy and by securing new market access for Japanese firms. Its loss has stripped Tokyo of a powerful tool and incentive to push China, which was not included in the deal, to adhere to regional economic standards. Indeed, with TPP dead, Abe must now look at alternative trade deals that offer weaker governance rules and fewer economic benefits, such as the Chinese-led Regional Comprehensive Economic Partnership.

As it deals with Trump’s protectionist stance, Tokyo might also be forced to consider entering negotiations over a bilateral trade deal with Washington to salvage some of the U.S. market-access concessions the TPP had promised it. And in their upcoming meetings, Abe will likely try to appeal to Trump’s apparent zero-sum approach to U.S. job creation: the prime minister reportedly plans to offer a suite of Japanese investment packages aimed at spurring U.S. job growth.


There has also been a great deal of concern over Trump’s foreign policy in South Korea. Seoul views the United States as a critical and longstanding ally in the defense of the Korean peninsula. As with Japan, Trump and his advisers have walked back some of their statements on mutual security in an attempt to reassure Seoul. Before Mattis’ trip, for example, Washington agreed to sell $140 million in missiles to Seoul to boost South Korea’s ability to deter North Korea. Similarly, Mattis agreed with his South Korean counterpart to proceed with this year’s deployment of the Terminal High Altitude Area Defense (THAAD) advanced anti-missile shield to South Korea, which will be used to defend against the North’s short and medium-range missiles. He also sought to soothe South Korea’s concerns by emphasizing that an attack made by the North would trigger an “overwhelming" response.

Washington’s decision to move ahead with THAAD was an important signal of the United States’ commitment to its alliance with South Korea and deterrence of the North. But deployment of the missile-defense system, which was agreed to during former President Barack Obama’s administration, will undoubtedly worsen relations between Seoul and Beijing. China sees THAAD as a U.S.-led attempt to hem in its strategic position—and as a betrayal of the closer ties it has developed with South Korea over the last five years.

The reality, however, is that THAAD is focused not on China but on North Korea, which has grown increasingly aggressive. Last year, Pyongyang conducted two nuclear tests and a host of missile tests. It is working to miniaturize nuclear warheads and has pledged to test an intercontinental ballistic missile this year. In the coming months, the Trump administration should continue to work closely with South Korea to improve deterrence against the North through THAAD, high-level diplomatic engagements, and increased trilateral cooperation with Japan.

A TV monitor showing U.S. President Donald Trump and Japanese Prime Minister Shinzo Abe at a foreign exchange trading company in Tokyo, February 2017.
Kim Kyung-Hoon / File Photo / REUTERS


The Obama administration’s pivot to Asia sought to draw the United States and its regional allies together through a web of bilateral alliances, trilateral dialogues, and multilateral structures, such as the TPP. Former Secretary of Defense Ash Carter described this approach as a “principled security network,” one by which the United States and its Asian partners could approach regional threats—from North Korea’s volatile regime to China’s assertiveness at sea—together.

Trump may prefer to rely on bilateral relationships, taking a tidier, more transactional approach. Yet nothing is more critical to East Asian security than the trilateral relationship among Japan, South Korea, and the United States. Indeed, because the United States’ interests in East Asia require collaboration and joint deterrence against shared risks, a bilateral approach to the region’s problems would fail. South Korea and the United States’ abilities to respond to a crisis on the Korean peninsula, for example, would be severely impaired without Japan’s help through intelligence-sharing and joint planning. This would be especially true if the North were to fire missiles at Japan, which hosts thousands of U.S. forces.

The relationship among Japan, South Korea, and the United States has made progress in recent years, with improved information-sharing, increased trilateral exercises, and frequent high-level political exchanges and dialogues. Mattis’ visit to Japan and South Korea affirmed this joint approach: His coupling of his trips to those countries was not a coincidence. Trump should take his meeting with Abe as another opportunity to reassure a vital partner that the United States needs its East Asian allies to help manage their region’s risky future.

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  • J. Berkshire Miller is an International Affairs Fellow at the Council on Foreign Relations, based in Tokyo, and a Senior Fellow on East Asia at the EastWest Institute.
  • More By J. Berkshire Miller