The US President is headed to South Korea on Tuesday, his second stop on an eight-day trip across Asia where the standoff with North Korea is likely to loom large.
The threat posed by North Korea's development of nuclear weapons and long-range missiles has been a top foreign policy priority for the Trump administration. The worry is that should Pyongyang successfully pair the two technologies, the reclusive country would have the potential to launch a devastating strike against a US city.
In the South Korean capital Seoul, Trump will find people who have lived with that reality for decades.
"It's crucial for Trump to show that he's willing to defend and protect South Korea because there's a lot of questions and concerns on the part of South Koreans about his commitment to that alliance, and that has fed fears here in South Korea that they may be abandoned," said Jean Lee, a global fellow at the Wilson Center and former Pyongyang bureau chief for The Associated Press.
Seoul has sat in range of North Korean artillery since the Korean War ended in an armistice in 1953. Experts believe that if war were to resume on the Korean Peninsula, the city would see tens of thousands of people killed in the first hours.
Many in South Korea, especially those who carry more liberal views, worry Trump's heated rhetoric, mocking and name-calling of North Korea's leader is exacerbating that danger.
A spokesman for the South Korean President's office urged citizens to warmly welcome Trump, though a handful of protests have been organized ahead of the visit.
"If he comes in here rattling his saber and using that sort of militant rhetoric, it's going to go down very poorly because this is the place that suffers the consequences," said John Delury, a professor of international relations at Yonsei University's Graduate School of International Studies in Seoul.
Trump won't visit the heavily-fortified demilitarized zone that separates North and South Korea -- foregoing what has been a symbolic opportunity for US commanders in chief to stare into the Hermit Kingdom -- declaring it a "little bit of a cliche."
'Trump's the wild card, not the reassurance guy'
By contrast, the South Korean government, led by President Moon Jae-in, will be looking to Trump for reassurance that the two countries are in this together, according to Van Jackson, a strategy fellow at the Centre for Strategic Studies at Victoria University of Wellington.
"Trump's visit is a huge variable. It's a great opportunity to show a unity of purpose against North Korea and reinforce the larger US commitment to Asia, but there's also a risk of provoking North Korea," Jackson told CNN in an email.
"We should brace for more heated rhetoric and some attempt to reassure South Korea. For most presidents, those tasks would not be mutually exclusive. The problem is Trump's the wild card, not the reassurance guy."
When he arrives in Seoul, Trump is scheduled meet with his South Korean counterpart, speak to service members from both countries and address the National Assembly in Seoul, according to the White House.
Trump's first Asia stop was in Tokyo, where he met Japanese Prime Minister Shinzo Abe. Those two have developed a good rapport and both share a hawkish stance toward Pyongyang.
Despite the fact that both the United States and South Korea continually stress the importance of their enduring alliance, Trump and Moon don't appear to share as close a relationship as Trump and his Japanese counterpart do.
Moon favors more engagement with Pyongyang and Trump's hard-line public stance on North Korea has added to the perception that a rift has opened up between the two men.
Trump's recent tweets saying that his Secretary of State, Rex Tillerson, is "wasting his time" on negotiations and another intimating Seoul was appeasing their northern neighbors likely didn't help.
"Hopefully Trump visiting Korea will give him greater appreciation of what's at stake in Korea in a human and war fighting sense if things go awry," said Jackson of Victoria University.
Trump will also come face-to-face with a South Korean public concerned they're being bypassed in the decision-making process when it comes to North Korea policy, according to Lee.
Those security fears have helped fuel a once-niche belief that is now gaining popularity: that South Korea needs its own nuclear weapons if it can't rely on the United States, though Moon has publicly ruled out that possibility.
A Gallup survey in September found 60% of South Koreans supported some form of nuclear capability for the country. At present, South Korea is defended by the US nuclear umbrella, a guarantee by Washington to defend the country in the wake of an attack.
"This is reflective of the sense of insecurity on the part of the South Koreans that they don't have that protection from the United States and the United States may be more willing under President Trump to really throw them under the bus," Lee said.
Trump is also seeking to renegotiate the US-Korea Free Trade Agreement, which experts believe could further strain the alliance at a time when they should be showing unity and resolve.
Quiet in Pyongyang?
Although Pyongyang has revived a threat to test a hydrogen bomb above the Pacific, the country has been relatively quiet when it comes to actions the United States considers particularly provocative: testing missiles and nuclear weapons.
Though Trump's visit would be an opportune time for Pyongyang to remind the world of its weapons program, experts were loath to make predictions about Kim Jong Un's intentions.
"They've been bathing in Trump's attention all year and I think they know that they are kind of the center of his trip. I think they will be tempted to act somehow to kind of remind everyone that they are an independent actor here and you can't just go to everyone around the neighborhood," Delury said. "Whether that means a missile test I don't know."
The US has been flexing its naval muscles in the region ahead of Trump's visit with three aircraft carriers conducting exercises in the Pacific for the first time since 2007.
Delury said, with Pyongyang quiet, US military maneuvers risk putting Washington in the role of provocateur.
"This is why Trump needs to show that they're serious about diplomacy and they're not just practicing gunboat diplomacy or aircraft carrier diplomacy," Delury said.
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