SEOUL — South Korean lawmaker Won Yoo-chul calls it “Trump risk” — the possibility that he will wake to a tweet from the U.S. president abruptly announcing the withdrawal of U.S. troops from the Korean Peninsula.

The concern is fueled by Trump’s demand that South Korea raise fivefold its payment for the cost of stationing U.S. forces in the country, and by what many here see as the president’s transactional approach to the alliance.

South Korea isn’t alone. Trump’s sudden decision to withdraw from border zones in Syria, undercutting the Kurds, has undermined trust in the United States and its commitment to other allies, from Israel to Taiwan and the Baltic states.

“If the United States withdraws its troops abruptly, our nuclear umbrella will disappear,” Won said. “What will happen to the safety of the South Korean people?”

Won and fellow opposition lawmaker Baek Seung-joo called in September for a new South Korean nuclear strategy, proposing that nuclear weapons be stationed in the country under the joint command of U.S. and South Korean forces, just as U.S. nuclear weapons are shared with NATO states.

Others have gone further, renewing the idea that South Korea will eventually be forced to acquire its own nuclear deterrent.

“President Trump is the most unpredictable head of state in the world,” Baek said. “I get concerned looking at the words Trump used when he announced the withdrawal of U.S. troops in Syria.”

'Should do more'

Over the past two years, Trump has returned to a central obsession: that South Korea, “a very wealthy nation,” is not paying enough toward the cost of stationing around 28,500 U.S. troops on the peninsula. 

In Singapore, after his 2018 summit with North Korea’s Kim Jong Un, he said he’d like to bring the U.S. forces all home “at some point,” while calling for an end to the “very expensive” and “provocative” joint-military exercises between the United States and South Korea.

Although his senior staff have tried to convince Trump that the troop presence also serves broader U.S. strategic interests, the president has — in the words of the State Department — “been clear that the Republic of Korea can and should contribute more of its fair share” of the costs.

“Our commitment to the defense of the Republic of Korea is ironclad,” said the U.S. ambassador to South Korea, Harry Harris, in an emailed statement. “Sustaining the costs of this commitment is not a burden that should fall on the U.S. taxpayer alone. While our alliances are in no way transactional, Korea, like other allies, can and should do more.” 

To his backers, Trump may have a point. Until 2010, South Korea paid more than half of the day-to-day costs of the U.S. troop presence, including the salaries of local staff working on the bases and other logistical costs. By 2018, that proportion had fallen to 41 percent, according to the United States Forces Korea Strategic Digest

But South Korea points out it also provides land for the bases rent-free, spends billions of dollars a year on U.S. military hardware, and provided 92 percent of the $10.7 billion cost of moving the main U.S. base out of Seoul to Camp Humphreys in Pyeongtaek, about 40 miles south of Seoul. 

Last year, South Korea refused to give in to U.S. demands for a big jump, agreeing only in February to raise its contribution by 8.2 percent, to around $900 million. But the deal was a stopgap, spanning one year rather than the usual five. 

North Korea factor

This time, the Trump administration is determined to get satisfaction. It has asked for a fivefold increase, Harris told the Dong-A llbo newspaper recently. That would imply South Korea is being asked to cover the entire $2.2 billion operations and maintenance budget, as well as another $2 billion for the salaries of the U.S. troops, according to Department of Defense budget figures.

Polls show most South Koreans support the alliance and U.S. troop presence, but few believe their country should pay more for the privilege. A group of ruling-party lawmakers said last month they would oppose parliamentary ratification of any deal that was “unfair” and unacceptable to the Korean people. 

The rhetoric from both sides is that theirs is a “relationship forged in blood” after the two militaries fought together in the Korean War of 1950-53. But Won and Baek, lawmakers from Liberty Korea Party, say that rhetoric is undermined by Trump’s relentless focus on money. 

“The United States Forces in Korea are not mercenaries,” Won said. 

Victor Cha, who served as President George W. Bush’s top adviser on North Korea and now works at the Center for Strategic and International Studies, warns of a scenario where Trump rushes into a bad nuclear deal with North Korean leader Kim, claims a “big victory,” and decides he doesn’t need so many troops in the South.

The removal of hawkish former national security adviser John Bolton makes this outcome more likely, he said.

 “And then the U.S.-South Korea cost-sharing negotiations fail. Then you might have this perfect storm where Trump says, ‘Okay, I have a deal with North Korea and you don’t want to pay. So I’ll pull the troops out, or a portion of the troops out,’ ” Cha said.

'Very much frustrated'

Congress built into the National Defense Authorization Act a condition that troop numbers in South Korea can only be cut below 22,000 provided the secretary of defense certifies that the step does not “significantly undermine the security of United States allies in the region,” and that those allies have been consulted. In that case, the best hope for preventing a large troop withdrawal might lie with Japan’s conservative Prime Minister Shinzo Abe, experts say.

Concerns about Trump’s commitment to defend South Korea grew this year after he dismissed North Korea’s ballistic missile tests as insignificant, despite expert assessment that the weapons were specifically designed to evade South Korean missile defenses

But the tensions in the alliance don’t only stem from the White House. 

Gen. Vincent Brooks, who retired as commander of U.S. Forces in Korea in January, notes a “rising progressive nationalism” in South Korea that doesn’t believe it should be “so connected, so dependent upon the United States for its security, both physically and economically.”

That’s embodied in the government of President Moon Jae-in, who angered Washington in August by withdrawing from a military intelligence-sharing pact with Japan.

The net result: Defense cost-sharing negotiations are more “politically charged” than in the past, with more direct involvement from both the White House and South Korea’s presidential Blue House, said Brooks, now a senior fellow at Harvard Kennedy School’s Belfer Center. 

Brooks says the alliance is strong enough to endure. But doubts are emerging. 

Moon Chung-in, a special adviser to the South Korean president for foreign affairs and national security, says many South Koreans are concerned that Washington is not making a genuine effort to resolve tensions on the Korean Peninsula, while simultaneously asking Seoul to pay more to host U.S. forces and buy more American military hardware. 

“On the one hand, American credibility is declining. On the other hand, America is demanding more money,” he said. “South Koreans are very much frustrated. And South Koreans will begin to have this deep suspicion of American motives.”