SEOUL – South Korea’s security alliance with the United States has provided the country with tremendous benefits for decades.

It remains hugely popular among the South Korean public, which likely explains why the left-leaning Moon Jae-in administration has been so accommodating of US policy under the erratic Donald Trump administration.

But as Washington squares off against a rising and assertive Beijing, Seoul is stuck in a precarious middle between its only strategic ally and its leading trade partner. It is a fight many in Seoul’s corridors of power would prefer not to take sides considering the political risks and economic costs.

Those risks are steeped in history. Communist China made it shockingly clear its sensitivity to US troops on its periphery in October 1950. That month, the Chinese People’s Volunteers Army made a shock intervention in the Korean War – routing advancing US-led forces and rescuing a collapsing North Korea.

North Korea endured and has since acted as a buffer on China’s northeastern frontier against democratic South Korea, the troops of its US ally, and the more distant Japan.

A strategic status quo has since held in Northeast Asia. Seoul and Beijing established diplomatic relations in 1992 and in 2015, the former Korean War adversaries signed a free trade agreement, albeit one with a 20-year implementation period.

But in recent years, a combination of North Korean brinksmanship, US troop redeployments in Korea and an escalating confrontation between Chinese President Xi Jinping, heading a newly assertive China, and US President Trump, leading an uneasy and uncertain America, is impacting this long-held dynamic.

As a result, South Korea is now being forced to confront the drawbacks, rather than simply the benefits, of its US alliance.

Yellow Sea re-alignment

When it comes to US military activities on and around the Korean peninsula, the key wake up call for Beijing came in 2010, a year of deadly confrontation in the Yellow Sea.

That year, a South Korean corvette was sunk by what Seoul insists was a North Korean submarine and North Korean artillery shelled a South Korean island. In a show of force aimed at North Korea, Washington sailed an aircraft carrier battlegroup into the Yellow Sea, a body of water that China considers its lake.

“2010 was a wake-up moment for China, it reconfirmed a long-held suspicion that the presence of US troops in South Korea is not just about North Korea, but also about China,” said Lee Seong-hyon, a China specialist at South Korean think tank the Sejong Institute.

“The battlegroup’s operational range is 1,000 kilometers. That is well beyond North Korea, that could send Tomahawk missiles to Beijing and Shanghai.” 

US infantry in Korea show off their equipment. The lockout of base workers is an unprecedented blow to the US alliance with South Korea. Photo: AFP

A more seismic – albeit, gradual – development was already underway: A major redeployment of US troops within South Korea that started in 2004 and would be completed in 2018.

For decades, the key locus of US troops in South Korea used to be the area between Seoul and the Demilitarized Zone (DMZ) that bisects the Korean Peninsula.

No longer. Today, only a token force of GIs is stationed on the frontier itself, at the truce village of Panmunjom. They are backed by a skeleton US infantry division – it only has one brigade, one third the strength of a normal division – in the town of Dongducheon, south of the DMZ and northeast of Seoul.

However, the bulk of US Forces Korea, or USFK, have abandoned the DMZ area, and departed their huge garrison at Yongsan in central Seoul. Their new home is beyond the range of North Korean tube artillery and tactical missiles on Korea’s west coast.

The vast new Camp Humphreys, 64 kilometers southeast of Seoul, lies inland from the Yellow Sea port and naval base of Pyeongtaek. It is the biggest American base outside the continental US and home to the busiest US military airfield in Asia.

Humphreys is not alone. It is sited between two pre-existing air and drone bases in the region, K9 and Osan.

In the big picture perspective, this means USFK has shifted from a predominantly east-west line of defense south of the DMZ, to a north-south axis that enfilades the lower reach of the Yellow Sea.

“Strategically speaking, Korea is very much a ‘lily pad’ and strategic promontory for the US,” said Alex Neill, a Singapore-based security consultant who specializes in the Chinese military. “It’s realignment on the west coast of the peninsula gives pretty good access across the Yellow Sea.”

There, the Chinese Navy’s Northern Fleet Command – charged with protecting Beijing, and fielding nuclear submarines and landing ships, among other assets – is based in the port city of Qingdao, west of Korea.

Another major Yellow Sea naval base and shipyard lies at Dalian, where China’s first indigenous aircraft carrier was built and where China’s naval academy is located.

Humphreys, which includes a walled-off National Security Agency (NSA) compound, as well as a string of US bases in its vicinity and a South Korean naval base that opened in 2016 on Jeju Island off South Korea’s south coast offer air and naval forces with excellent balconies.

Officers quarters and a sports ground at the sprawling Camp Humphreys. The base, near Pyeongtakek, South Korea, is the largest US garrison outside the United States. Photo: USFK

From there, they can monitor the assets of China’s expensive new blue-water navy as it exits the Yellow Sea and steams for the open Pacific.

“A US forward presence on the westward periphery of the Korean peninsula gives eyes, ears and reach,” said Neill. “All you have to do is look at some of the flight-tracking data that China is producing in open source-intel: There are a great number of reconnaissance operations mounted along China’s periphery from South Korea.”

Korea’s costs

South Korean taxpayers paid 90% of the $11 billion cost of the giant 3,454-acre Camp Humphreys.

Naturally, much of that cash went to South Korean contractors, and much of it could feasibly be recouped thanks to the real estate value of Yongsan Garrison, the now virtually deserted US base in central Seoul when it is fully returned to South Korean ownership. 

But ensuring Humphreys’ survivability is arguably costing South Korean businesses more.

In July 2016, Washington and Seoul agreed to emplace a THAAD (Terminal High-Altitude Area Defense) anti-missile system to back up the Patriot systems based at Camp Humphreys to protect US forces and civilians south of Seoul amid North Korea’s evolving threat.

The battery was rushed into position in 2017, amid political turmoil in South Korea. The government that agreed to THAAD’s emplacement had been impeached and the incoming Moon administration was more cautious about the deployment.

It was furiously protested by China, which fumed that THAAD’s powerful radar could snoop on its own strategic weapons.   

The basing of US anti-missile assets in Eastern Europe has long been a bugbear for Moscow. Even non-Chinese experts concede that, for the same reason, Beijing has a real argument when it comes to THAAD.

“When I was first looking at this argument, sources from the US were saying THAAD does what it is designed to do … to look into the North to detect missile launches,” said Neill. “But there is the ‘five minutes and a screwdriver argument’ – you could potentially very quickly place assets on the western periphery bases that could point into China.”

“One of the main reasons why China was so incensed over the THAAD deployment in South Korea is that it challenged their ability to dominate using missile threats and took away any surprise operation by China because of the long-range radar which is part of THAAD,” said Stephen Bryen, a former staff director of the US Senate Foreign Relations Committee and deputy under-secretary of defense for Trade Security Policy.

This US Department of Defense/Missile Defense Agency handout photo shows two THAAD interceptors and a Standard-Missile 3 Block IA missile being launched. Photo: AFP/DoD/Missile Defense Agency

In retaliation against THAAD, China opened a new front deploying economic rather than military means. And the target was not the US, but South Korea.

Lotte Group, which supplied the land for the THAAD battery, faced boycotts in China, and eventually exited retail operations in the country. Korean auto sales in China plunged. Chinese group tourism to South Korea – its largest contingent of foreign visitors – was halted.

And K-pop and K-drama sales to China were halted. That means that, despite the popularity of K-pop in China – indeed, the widely-used term Hallyu (“The Korean Wave”) is Chinese – the uber-K-pop band, BTS has never played in China.

To assuage China, Moon, in a summit with Xi in Beijing in October 2017, agreed to “Three No’s:” No further THAAD deployment; no Seoul-Tokyo-Washington military alliance; and no participation in a future cross-Pacific US missile defense system.

That restored an uneasy peace in diplomatic relations, but now it appears that the US is leaning on South Korea with regard to the third of the “no’s.”

In September, Marshall Billingslea, the US presidential envoy for arms control, visited South Korea where he reportedly briefed his hosts on China’s growing missile forces. 

According to the Chosun Ilbo, South Korea’s leading newspaper, Billingslea called China a “nuclear-armed bully,” said it was a moral duty to defend the US mainland and “expressed hope that Seoul and Washington will work together in this task.” 

And in a non-military development, also in September, South Korea suffered further collateral fallout as a result of its alliance with Washington.

Amid the cross-Pacific trade war and related US sanctions, the country’s semiconductor giants Samsung Electronics and SK Hynix are suffering the loss of chip sales to Chinese tech flagship Huawei – and very possibly other Chinese companies in the future.

According to the partly state-run Yonhap news agency, the two South Korean chipmakers could suffer 10 trillion won ($8.45 billion) in lost revenues if US sanctions remain in place for a year. That amounts to approximately one-tenth of South Korea’s overall chip exports in 2019 of $93.93 billion, Yonhap stated.

Korea’s risks

The GI’s footprint in Korea offers America more than just its foremost operating base on the Asian mainland.  It is also the front line in a phased defense of the US mainland.

The premier US ally in East Asia is Japan. Should South Korea fall, then Japan is suddenly a front line. “If the Korean peninsula falls under inhospitable influence, then Japan is in jeopardy,” said Chun In-bum, a retired South Korean general. “And if Japan goes, all of the North Pacific goes and the US loses freedom of action in the Pacific.”

From South Korea and Japan, the US has a layered defense network that stretches back across the Pacific through Guam, Wake Island and Hawaii. For virtually any form of physical defense – be it missile, aero-spatial or naval – this huge expanse provides a priceless barrier that any enemy asset must cross before reaching American soil.

“If there is a conflict between the US and China, the South Korean contours of the Yellow Sea would be the first line of offense and defense for the US,” said Lee. These dots connect each other [and] China is very conscious about these things and nobody is blind to the implications of these dots.”

That massive “if” is all-too-real for South Korea.

Chinese People’s Liberation Army Navy (PLAN) shipmen during a maritime operation. Photo: AFP via Getty

While the terms of their mutual defense treaty do not automatically demand that one government assist the other in the event of a confrontation, if bullets fly there are weighty legal-political imperatives for Seoul in some way, shape or form to take America’s side.

“The mutual defense treaty is not just about defending South Korea, but also about defending the United States,” said Lee.  “We tend to think it is all about North Korea but it is mutual, it cuts both ways.”

And the treaty’s terms are not restricted to the peninsula.

“An underreported aspect of the treaty is the coverage is not just the Korean peninsula, the vocabulary is ‘The Pacific,’” Lee continued. “If there is a war in the Pacific, the US and South Korea will mutually help each other.”

These costs and risks all add up for Seoul.

“If South Korea or Japan concludes that the American bases put them in the crosshairs of either China or North Korea, there may be growing pressure for asking the US to leave,” said Bryen.

Indeed, there were protests against the construction of Camp Humphreys and the Jeju naval base, as well as against THAAD’s deployment. But at a time when Japan has done a surprise u-turn on the deployment of an Aegis Ashore missile defense system, South Korea has held firm in its various commitments to Washington.

This could be related to public perceptions in South Korea. Beijing’s THAAD retaliation sent shockwaves across the body politic. So, too, did Beijing’s crackdown on Hong Kong, among a public with living memory of local pro-democracy struggles in the 1980s. 

According to public opinion watcher James Kim of the Asan Institute, the US remains far more popular than China among ordinary South Koreans.

In a bilateral relationship as long, complex and multi-faceted as that between Seoul and Washington, it is impossible to do a zero-sum, dollar-cost analysis that would prove which side has the greater benefit.

South Korean marines patrol on the South Korea-controlled island of Yeonpyeong. Photo: AFP / Yonhap

And the changed shape of an alliance that for half a century existed simply to deter a North Korean attack across the DMZ may not be fully recognized by either South Koreans or Americans.

South Koreans may not fully recognize that the GIs on its soil are now there to defend the US as well as South Korea from North Korea, which has recently gained the capacity to hit mainland America with its missiles.

Similarly, Americans may not realize the price that South Korea is paying for its alliance with the US as Washington’s global rivalry with China heats up. In that sense, strategists are gobsmacked that Trump, who is demanding a near 500% annual increase in stationing costs from South Korea, is apparently blind to the advantages South Korean real estate offers America.

“Given how little the US pays for maintaining bases and how many security benefits, both present and potential, that the US has by having troops stationed in Korea, it is mindboggling and peculiarly curious that the president of the US cannot see this geopolitical strategic logic,” said Neill, a specialist in China’s armed forces.

“For the US, the clearest manifestation of a superpower’s sphere of influence is to have troops in a foreign country,” said the Sejong Institute’s Lee. “That symbolizes that the US is a superpower – and its influence and defense line.”

US commitment to South Korea certainly has implications for America’s regional reputation.

“For public diplomacy and soft power purposes, it is key for the US to send a continuing, sustained signal of deterrence,” said Neill. “If the administration wants a US troop reduction, it can be done – but why now when China’s influence is rising and the perception is that US power is declining.”

Moreover, South Korea’s zero-to-hero success story is a shining example of US power and influence put to good use, one that contrasts sharply with subsequent failures in Vietnam and Iraq, and one that is worth defending rather than alienating.

“I’d say that what the US has been able to do in South Korea is the best example of what the US can do as a contribution to the betterment of the world,” said Chun In-bum, a retired South Korean general.