SEOUL, South Korea—“If the United States believes that it doesn’t need an alliance with the Republic of Korea, I would say it’s okay. If the United States doesn’t want the alliance, we don’t have to beg for it.”

It was a stunning statement to hear in Seoul from one of South Korea’s highest-ranking officials, considering it was in regard to a nearly 70-year partnership forged by American and Korean soldiers who fought and died together during the Korean War. And it was a sign that well beyond South Korea, the United States’ system of alliances is buckling under pressure from President Donald Trump’s campaign to renegotiate the terms of America’s involvement with the world—to turn what used to be a basic tenet of U.S. grand strategy into a blunt question of financial grand totals. Seated in his ornate chambers in April, the speaker of the National Assembly, Moon Hee-sang, was answering my question about Trump’s demand for South Korea to shell out more money to keep American troops in the country, and his threats to impose tariffs on South Korean goods.

Just as striking as Moon’s comment was the context in which he said it. South Korea “was able to become what it is today thanks to the support of the United States,” he noted with appreciation in our interview, in remarks that were translated. But now, as one of the world’s top economies, it is prepared to “pay back” the international assistance it received by helping “share the burdens” of resolving global problems.

From the presidency of George Washington through World War II, American leaders shunned open-ended, entangling alliances with other countries. But that all changed after 1945, as the United States sought to avert another earth-shattering conflict and counter the Soviet Union by fashioning a new, U.S.-friendly international order. Washington established collective-defense treaties with numerous far-flung countries and military bases across Asia and Europe.

Trump, however, doesn’t seem to buy the argument that animated his Republican and Democratic predecessors: that the defense of U.S. partners is also a defense of U.S. interests in strategically vital regions.

Moon’s remarks had the perhaps unintended effect of underscoring Trump’s fundamental complaint about America’s military posture in the world. And his grievances are playing out most prominently with South Korea, which is now a testing ground for whether the U.S. overseas military presence will endure or unravel. The two sides are due in the coming months to start hashing out a new agreement on Seoul’s contribution to funding the 28,500 U.S. troops deployed there to deter North Korean aggression and act as a counterweight to China.

But this is much bigger than just a numbers game with South Korea. If these talks fail and future negotiations with other allies collapse as well, it could potentially precipitate withdrawals of U.S. forces, constrain America’s capacity to project power globally, and encourage partners to embark on their own defense buildups and more independent foreign policies. All of which would scramble geopolitics in Asia, Europe, and the Middle East, at a time when the Trump administration has staked out the strategic goal of competing with powers such as China and Russia for supremacy in the 21st century.

South Korea, moreover, isn’t just any old ally. Its formidable military is arguably more intertwined than that of any other country with America’s. It hosts the third-largest contingent of overseas U.S. troops, a presence that has persisted (if in diminishing form) since the countries signed a mutual-defense treaty following the Korean War. It bankrolled the construction of a new headquarters for American forces in the country that ranks as the largest overseas U.S. military base on the planet. It is one of the world’s biggest buyers of U.S. arms and home to a U.S. anti-ballistic missile-defense system. The point of the American military presence in South Korea, former Defense Secretary James Mattis once reportedly informed Trump, is to “prevent World War III.” The United States could be said to have some skin in the game on the peninsula.

Despite all that, contentious burden-sharing negotiations between the United States and South Korea concluded earlier this year in a fleeting deal that needs to be either extended or renegotiated before the end of 2019, with Trump backing down from his request for a huge hike in what Seoul pays to maintain U.S. troops in South Korea.

The next round of talks will signal where Trump, who’s gunning for a second term, stands on alliances. Nations that partner with the United States will be watching the proceedings closely to see what new demands the president makes of South Korea. The most likely outcome is that the parties strike some sort of compromise. But should the improbable happen, it could prove world-changing. If the U.S. prevails on South Korea to overhaul their agreement, that could produce a paradigm shift in America’s defense arrangements with allies. If the parties reach no agreement, that could lead to an alliance-threatening move such as a drawdown of American troops. Japan, the largest host of forward-deployed American forces, is set to begin its own talks with the United States on a cost-sharing agreement that lapses in 2021. Germany, the second-largest, regularly earns Trump’s wrath for not spending enough as a NATO member on defense.

Ever since the late 1980s, Trump has been expressing what appears to be among his most firmly held convictions: Countries such as Germany, Japan, Saudi Arabia, and South Korea have gotten rich at America’s expense, drawing on U.S. military might to safeguard their economic expansion rather than having to divert resources to defend themselves like the United States does. He has argued with remarkable consistency that it’s time for the United States to either get paid top dollar for the services of the finest fighting force in the world, whose presence he believes is a bigger boon to allied countries than it is to the U.S., or bring American soldiers home.

“The Japanese have their great scientists making cars and VCRs and we have our great scientists making missiles so we can defend Japan,” he fumed in a 1990 Playboy interview. “Why aren't we being reimbursed for our costs?” he asked, arguing that the U.S. Navy was foolishly protecting Japanese ships transporting oil from the Persian Gulf to Japanese car factories that then fiercely outcompeted their American counterparts.

The president is “a balance-sheet person” who is “not as sympathetic to, or aware of, the less tangible benefits of [an] alliance: access and overflight and the psychological benefits,” said one former Trump-administration official, who spoke on condition of anonymity to discuss the issue. Trump’s attitude is, “‘Hey, if you guys aren’t going to pay your share, why the hell should we come and save your ass?’ That’s what he’s thinking.”

Trump has repeatedly indicated that when it comes to South Korea’s share, he has a very big number in mind. At recent rallies in Florida and Wisconsin, the president, who is slated to visit South Korea in June, boasted of how he’d personally called the leader of an unnamed country and compelled him to double the country’s $500 million contribution to offset the $5 billion cost of stationing U.S. troops there. “We lose four and a half billion dollars to defend a country that’s rich as hell and probably doesn’t like us too much,” he said in Florida.

Assuming he was speaking about South Korea, which he most likely was since he’s previously used the exact same figures in reference to the country, the statistics were all off. Seoul had been chipping in more than $800 million (not $500 million) prior to the last round of negotiations as part of a regularly renewed cost-sharing agreement that covers wages for Korean workers at U.S. military installations, along with construction and logistics expenses. In February, the South Korean government agreed to modestly increase (not double) its contribution by 8 percent to a sum amounting to 41 percent of the “day-to-day non-personnel-stationing costs for U.S. Forces Korea,” according to the U.S. Defense Department. The Pentagon’s estimate suggests the total for expenses governed by the cost-sharing pact, which does not cover matters such as wages for American troops or bills for alliance-related U.S. military operations, is roughly $2 billion.

Yet the inaccuracies in Trump’s comments were revealing. In pegging the total expense for the hosting of U.S. troops at $5 billion rather than $2 billion, and characterizing all U.S. expenditures on its troops in South Korea as pure loss, Trump was making something clear: He is not evaluating the costs and benefits of America’s overseas military presence the way U.S. officials traditionally have. Fact-checking his figures is like calling out infractions of established grammar by a man inventing a new language.

Procuring “military protection” money from wealthy allies, Trump informed his cheering supporters in Wisconsin, would prove “easier” and “safer” than collecting rent from tenants in rough neighborhoods of New York City.

Soon, he vowed, apparently addressing South Korea, “we’re going to call you for much more.”

A simmering concern in Seoul, as the South Korean newspaper Hankyoreh encapsulated it, is that in insisting earlier this year on an unusually short-term burden-sharing deal, the Trump administration was “trying to buy time” to develop “a sweeping strategy of readjusting the framework of defense-cost sharing by American allies around the world.”

Asked whether the Trump administration is indeed conducting a systematic review of its military burden-sharing arrangements, the National Security Council spokesperson Garrett Marquis declined to comment on “any ongoing deliberations regarding specific ideas” about how to get “allies to increase their investment in our collective defense and ensure fairer burden-sharing.”

In March Bloomberg reported on one of the ideas that might be under deliberation: asking Germany, Japan, South Korea, and other countries to pay the full expense of maintaining American soldiers on their soil plus a 50 percent premium, a formula known as “Cost Plus 50” that the president initially pursued during the most recent round of talks with Seoul. Bloomberg noted that the plan might feature new cost categories, such as host nations covering the salaries of U.S. troops.

Cost Plus 50, which would require South Korea to pay at least three times what it is now, is “unthinkable,” Lee Soo-hyuck, a lawmaker with the governing liberal party and a member of the National Assembly’s Foreign Affairs and Unification Committee, told me in April, just days after the National Assembly ratified the one-year cost-sharing agreement. (The legislature would need to approve any future deals with the United States as well.)

For now, South Korean officials are taking solace in the denials of such a plan by Acting Defense Secretary Patrick Shanahan and the absence of any formal U.S. request for such an amount.

“We get a lot of indicators” that American negotiators won’t be asking South Korea to pay full cost plus a premium, said a senior South Korean official who met with U.S. officials in Washington, D.C. this spring and spoke about the consultations on condition of anonymity.

Noting that he’d heard Cost Plus 50 was “fake news,” Moon, the National Assembly speaker and a member of the president’s party, nevertheless warned that if the Trump administration pressures South Korea to pay the full cost of U.S. troops stationed in the country, the Korean people might think, “‘U.S. troops are just mercenaries hired by the Korean government and they are here just to make money,’” which could turn public opinion against the United States.

Multiple South Korean officials whom I spoke with, in fact, expressed concern that Trump’s transactional approach to the alliance could stoke anti-Americanism. Eighty percent of South Koreans had a favorable view of the United States as of 2018, one of the highest levels of favorability among countries surveyed by the Pew Research Center. Confidence in the U.S. president, however, has declined from a high of 88 percent under Barack Obama to 44 percent under Trump.

Heading to the office of the National Assembly member Won Yoo-chul, a top voice on national security with the main opposition conservative party, I expected to find someone who would downplay the burden-sharing tensions as mere haggling in a military partnership that must be upheld at any cost.

Won is a hard-liner on North Korea—a proponent of redeploying American tactical nuclear weapons to South Korea. He’s also an advocate of sticking with the U.S. alliance despite pressure from China, once staging a one-man protest outside the Chinese embassy in Seoul when Beijing retaliated economically against South Korea for deploying an American missile-defense system. His constituency includes the U.S. Air Force’s Osan Air Base.

Yet Won told me through an interpreter that given Trump’s burden-sharing stance, diplomatic overtures to Kim Jong Un, and suspension of major U.S.–South Korea military exercises, he is “very concerned” about the U.S. alliance for the first time in his two decades of service in the National Assembly.

Won referenced reports from South Korean officials that during the last round of talks, American officials had asked Seoul to help cover additional expenses such as the cost of deploying U.S. nuclear-capable military assets near the peninsula. (South Korea declined to assume the new expense, for the time being.)

He also feared that in nuclear talks between the United States and North Korea, Trump and Kim would have “mutual interests” in reducing the U.S. troop presence on the peninsula.

“Unreasonable American demands make the South Korean public question” the rationale for sustaining the alliance in the first place, Won explained, leaving him and other politicians who prioritize the partnership with the United States in a “very difficult position.” (Such requests would likely trigger similar debates in Germany and Japan, where larger segments of the population than in South Korea are already critical of the military alliance with the United States.)

Invoking a Korean proverb, Won suggested that the hundreds of millions or perhaps several billions of dollars in dispute between the two countries was pocket change relative to the value of the alliance.

“Don’t lose big over a desire for a small thing,” he warned the Trump administration.

Ever since Dwight Eisenhower called in 1952 for U.S. troops to remain in Europe for only 10 years, lest partners become “flabby dependents,” U.S. presidents have been prodding allies to assume more responsibility for their own defense. Well before Trump’s “We are getting ripped! We’re defending the world” came Eisenhower’s “We cannot be a modern Rome guarding the far frontiers with our legions.”

Richard Nixon sought to shift burdens to allies at the end of the Vietnam War, and George H. W. Bush tried to do the same as the Cold War wound down. John F. Kennedy and Lyndon B. Johnson, in Trumpian fashion, used the threat of U.S. troop withdrawals as leverage to attain economic concessions from NATO states. Barack Obama complained that his ranks were rife with “free riders.” The question “Why should the United States, with its huge deficits, keep paying to protect a country whose surpluses pile up by the day?,” which could easily appear in The Atlantic’s pages today, actually comes from an article by my colleague James Fallows that described the prevailing view of Japan in Washington, D.C., circa 1989.

U.S. investments in its alliance system, moreover, have always been predicated more on unsentimental self-interest than selfless devotion to the values it shares with its partners. The foundation of U.S. foreign policy, Eisenhower argued, was securing access to raw materials and lucrative foreign markets. U.S. leaders have repeatedly consented to take on a greater share of the military burden of alliances than their allies, however grudgingly, in part because that has allowed them to retain some measure of control over those countries.

Trump, however, has gone much further than previous presidents. He frequently states that prosperous U.S. allies pose a greater threat to the nation’s interests than some of its adversaries, because they have sapped the United States of its strength by extracting security obligations and free-trade deals. Which is why Trump claimed at his Florida rally that America’s “rich as hell” military partner “doesn’t like us too much.” He rarely mentions the ways in which America’s collective-security networks have accrued to its advantage, such as when NATO members came to the defense of the United States after the 9/11 attacks. Nor does he pay heed to evidence that the country’s security commitments are a net benefit for the U.S. economy.

It’s not that Trump wants partners to merely invest more in a mutually beneficial alliance with the U.S. It’s that he wants these partners to pay a lot because he believes that otherwise the United States gets little out of the relationship. Money was once the sideshow. Now it’s the main show.

Among the challenges of this approach is that it’s difficult to develop a methodology for calculating both sides’ costs. The Pentagon estimates that it currently spends more than $20 billion a year on its overseas military presence—mostly in Germany, Japan, and South Korea, but also in nations as disparate as Australia, Italy, Kuwait, and Djibouti—and allies defray the cost in different ways and to different degrees. How, for example, should a country’s purchases of U.S. weapons factor into the equation?

If, moreover, Trump turns these calculations into steep financial demands, allies will push back by arguing that the overseas troop presence serves U.S. interests as well as their own. In South Korea and Japan, for instance, one of the roles of American troops is to keep China in check and maintain stability in one of the most vibrant and volatile parts of the world. U.S. Africa Command is headquartered in Germany, as is a medical center that has provided emergency care to U.S. soldiers wounded in Iraq and Afghanistan.

Germany helps bear the expense of stationing more than 30,000 American troops in the country through in-kind contributions such as land and infrastructure. In an interview in January, German Ambassador Emily Haber cited the example of a road built for the U.S. military that also benefits Germans to illustrate how hard quantifying the cost of the setup can be.

When it comes to how Germany can better share the burdens of their military alliance, Haber told me, the U.S. Defense Department has been concentrating on the country’s efforts to improve its military readiness. But the focus from elsewhere in the Trump administration has been “numbers. Only numbers.”

In fixating on numbers and dramatically rethinking America’s military footprint abroad, it’s possible Trump will succeed in obtaining more money from resistant allies than his predecessors did. But “the concern about the Trump presidency is that he’s destabilizing the liberal international order and making us question whether the U.S. will be here for a long time,” says Park Cheol-hee, an East Asia scholar at Seoul National University. “We question, question, question.”

Hence why there has recently been a flurry of bipartisan activity in the U.S. Congress to construct various (not insurmountable) hurdles to Trump exiting NATO and pulling U.S. troops out of several countries, including South Korea.

The U.S. president could scale down the American military presence in South Korea not just if cost-sharing talks go awry, but also as part of a peace deal should North Korea ever agree to give up its nuclear weapons. For now, however, the South Korean government welcomes Trump’s diplomacy with Kim.

“In Korea people say—I’m just quoting from people—that ‘President Trump is both a blessing and a curse,’” observed Moon Chung-in, a foreign-policy adviser to South Korea’s president who said he was speaking in his unofficial capacity as a university professor.

He’s “a blessing for the North Korea nuclear issue because he wants a negotiated settlement,” explained Moon, one of the intellectual architects of the current president’s policy of engagement with Pyongyang. “But he’s a curse for defense-cost sharing and the future of the R.O.K.-U.S. alliance.”

One rainy day in Seoul this spring, I came across a group that remained singularly upbeat about Trump’s commitment to the military partnership. Right-wing activists who lionize the impeached conservative president Park Geun-hye had gathered for their weekly protest at the gate of a 17th-century palace downtown. Dozens of mostly older Koreans sat on stools, sipping ginseng tea and listening to an impassioned speaker on a stage draped with images of Park and Trump and a stark message to the South Korean president: “You are destroying the US-KOREA Alliance, our right for survival.”

A man sporting a sticker of linked South Korean and American flags on his cheek strode up to me. “We love U.S.A. and Mr. Trump,” he declared, denouncing the “leftists” in the ruling party who he claimed want the “Yankees [to] go home.” American soldiers “help us, so we have to pay some [more] money,” he told me.

When I asked whether he was worried about the American president removing U.S. troops from the peninsula over a financial dispute, the man paused, shot me a perplexed look, and then grinned. “Anyway,” he said, “we love U.S.A. and Mr. Trump.”


Peter Nicholas contributed reporting from Washington.

Reporting for this story was made possible in part by the Atlantic Council Korea Journalist Fellowship Program. The fellowship was sponsored by the Atlantic Council, a nonpartisan think tank in Washington, D.C., in partnership with the Korea Foundation.