A U.S. Republican presidential candidate Donald Trump campaign poster is seen on the seats at a campaign event in Milwaukee, Wisconsin, United States, April 4, 2016.
Jim Young / Reuters

Donald Trump, the leading Republican candidate for this fall’s presidential election, has been no stranger to controversy. Washington’s longstanding relationships with its key Northeast Asian allies—Japan and South Korea—were among his recent targets. In an interview last month with The New York Times, Trump questioned the value of the alliances with Tokyo and Seoul, accusing those countries of benefiting from Washington’s security guarantees and offering little in return.

Trump further insisted that the United States should think about withdrawing its forces from both Japan and South Korea—more than 80,000 troops in total—unless Washington’s Asian allies “pay more” for their housing. To cap things off, Trump suggested that both Japan and South Korea consider developing an independent nuclear weapons capacity as a potential solution to regional security threats posed by North Korea.

The notion of abandoning the alliances with Japan and South Korea, which have served U.S. interests remarkably well over the past several decades, has been met with concern and surprise in Seoul and Tokyo. Japan’s Chief Cabinet Secretary insisted that, no matter whom the United States elects later this year, the alliance with Washington would remain the “core of Japan’s diplomacy.” The influential liberal newspaper Asahi Shimbun evaluated Trump’s remarks as “bewildering” and having “caused unease” in political and diplomatic circles in Tokyo. South Korea has expressed similar frustrations, with the Joo Ang Daily noting that such suggestions would “destabilize regional security.”

U.S. President Barack Obama and Japanese Prime Minister Shinzo Abe visit the Lincoln Memorial in Washington, with the Washington Monument in the background April 27, 2015.
U.S. President Barack Obama and Japanese Prime Minister Shinzo Abe visit the Lincoln Memorial in Washington, with the Washington Monument in the background April 27, 2015.
Kevin Lamarque / Reuters
In truth, it is nonsensical to suggest that U.S. allies in Northeast Asia take on more of the burden for the U.S. bases there. Japan and South Korea already pay the lions-share of costs of constructing new bases and infrastructure in their countries. Further, as U.S. Ambassador to South Korea Mark Lippert recently noted, Seoul continues to pay for more than 55 percent of non-personnel costs. In Japan, Tokyo is on the hook for 100 percent of the cost of replacing the controversial Futenma base in Okinawa. Japan has even offered to pay more than a third of the costs—totalling more than $3 billion—to move U.S. forces to Guam (which is a U.S. territory).

The idea of going nuclear is also illogical. Last week, U.S. Deputy National Security Advisor Ben Rhodes remarked that the spread of nuclear weapons in Northeast Asia would be “catastrophic” and would “indicate that we somehow support the proliferation of nuclear weapons.” U.S. President Barack Obama went even further in dismissing Trump as a foreign policy amateur and stressing that the alliances with Japan and Korea represent the “cornerstone” of the American presence in Asia and help to underwrite Washington’s security and prosperity. Indeed, the United States has deployed 60 percent of its navy to the Pacific and three of its top six trading partners are in Northeast Asia: China, Japan, and South Korea.

But, as fallacious as Trump’s comments on Washington’s alliances are, they do shed light on a critical issue for the next administration’s foreign policy: re-affirming and bolstering U.S. strategic links with its Asia–Pacific allies, which is especially important in an increasingly volatile security situation in North Korea and in light of the sustained challenge of China’s maritime brinksmanship. The Obama administration’s policy of rebalancing to the Asia–Pacific has been—and continues to be—premised on the idea of reassuring Washington’s allies that the United States will remain a Pacific power for decades to come. The policy, which has been critiqued as both too aggressive or too feeble (depending on the party or capital one asks), also looks to U.S. allies in the region to strengthen their own commitments to upholding a prosperous and rules-based order in a region that will continue to thrive despite simmering tensions over territory and resources.

In order to add teeth to the rebalance, the Obama administration has formulated a diplomatic, security, and economic approach. The diplomatic arm has involved an uptick of high-level engagement by senior officials in the region. The economic pillar has been centered on the Trans-Pacific Partnership (TPP), a 12-member regional trading pact that was signed earlier this year and upon ratification would cover nearly 40 percent of the world’s gross domestic product. The security component has, thus far, been the most successful highlighted by enhanced partnerships and strengthened military ties with allies such as Australia, Japan, the Philippines, and South Korea.

Shared security concerns remain one of the key foundations for the U.S. presence in Northeast Asia. Last week, on the sidelines of the capstone Nuclear Security Summit held in Washington, U.S. President Barack Obama stood shoulder to shoulder with Japan’s Prime Minister Shinzo Abe and South Korean President Park Geun-hye as the three sides discussed ways to enhance their trilateral partnership. Their main focus remains North Korea, which continues to build its nuclear weapons and missile capabilities despite an array of sanctions against the regime. Pyongyang has consistently repudiated efforts by the United States, Japan, and South Korea to de-nuclearize and has enshrined its nuclear status as a pillar of national pride.

U.S. President Barack Obama and South Korea's President Park Geun-hye hold a joint news conference in the East Room of the White House in Washington October 16, 2015.
U.S. President Barack Obama and South Korea's President Park Geun-hye hold a joint news conference in the East Room of the White House in Washington October 16, 2015.
Jonathan Ernst / Reuters
Despite this, Washington, Tokyo, and Seoul are not always reading from the same sheet of music, largely due to strained relations between Japan and Korea over historical issues. Last December’s deal between Seoul and Tokyo on the so-called “comfort women,” while not perfect, has re-opened a window for stronger bilateral and trilateral cooperation. The failures of diplomatic isolation and the lack of good options on the use of force in North Korea underscore the value of “joint deterrence,” a mixture of both U.S. security guarantees to its allies and also the build up of adequate deterrent capabilities and policies by Seoul and Tokyo.

North Korea’s threats to Seoul and Tokyo directly endanger U.S. interests. Even if the regime’s claims to have functioning long-range missiles are dubious at best, Pyongyang has long maintained a large arsenal of accurate short-range missiles that could target Japan and South Korea, including the bases that house U.S. forces in both countries. These threats cannot be mitigated through an isolationist approach of fishbowl diplomacy that Trump advocates. Rather, the United States relies on its key allies just as much in order to secure and protect its interests of a stable security environment with vibrant trade and growing economic dynamism. If Washington were to lose its bases in South Korea and Japan, its ability to effectively respond to North Korea in a crisis scenario would be severely limited. Magnifying these concerns is the fact that time would be of the essence considering that Pyongyang has more than 13,000 pieces of artillery near the demilitarized zone, which is only 35 miles away from Seoul.

In addition to the threat posed by the North is the immediate but also sustained challenge of China’s rise and ensuring that Beijing adapts to well-established norms and rules in the region. This is a vision of the Asia–Pacific that Washington shares, but is effectively underwritten by its East Asian allies. U.S. retrenchment in Northeast Asia would almost surely be swallowed up by Beijing and would set off an arms race in the region. Such abandonment would also severely limit Washington’s naval posture and ability to promote and enforce the freedom of navigation and rules-based order that it so often highlights.

But the value of U.S. alliances with Japan and South Korea exceeds hard security challenges. The relationships built and nurtured since the end of World War II have supported U.S. commerce and trade in the region. In addition to the TPP, which includes Japan, the United States also has a free trade agreement with South Korea that went into force in 2012 and that adds more than $10 billion annually to U.S. GDP. And despite a long running trade deficit with Japan, the United States benefits from $60 billion in exports to Japan and billions in foreign direct investment that facilitates and builds sustainable employment stateside.

The policy of rebalancing to the Asia–Pacific belongs to the Obama administration. The goals and underlying justification for the policy, however, transcend party lines and presidential terms. Trump’s GOP rivals admit that Washington’s alliance structure is critical to the region’s future. John Kasich labelled the Japanese–U.S. alliance as “essential” and Ted Cruz, despite slamming Obama on the TPP, has warned about regional states in Asia moving away from Washington and toward Beijing. Simply put, Washington’s prosperity and security is—and will continue to be—deeply interlinked with East Asia’s. Without the partnership and longstanding security alliances with Japan and South Korea, both futures look dark and uncertain. To think otherwise demonstrates more than benign ignorance and threatens U.S. interests and credibility in this critical part of the world.