As Donald Trump returns to the White House for a second term, the world is reminded of his high-stakes, often unpredictable approach to diplomacy, especially regarding the Korean Peninsula. During his first term, Trump navigated one of the most volatile relationships in US foreign policy with North Korea, combining tough sanctions, blunt rhetoric and unprecedented summits.

Trump's administration initially took a confrontational approach to North Korea, especially after Pyongyang conducted its first intercontinental ballistic missile test in July 2017. Trump responded with "fire and fury" rhetoric, opting for a "maximum pressure" stance that escalated tensions on the world stage. Sanctions were intensified to curtail North Korea's economy and pressure Pyongyang to halt its nuclear ambitions.

By 2018, Trump’s confrontational stance turned the page to an unexpected chapter. In a historical twist, Trump became the first sitting US president to meet with a North Korean leader when he shook hands with Kim Jong-un at the Singapore Summit in June 2018. While the meeting was a landmark diplomatic gesture, the resulting agreement was nonspecific and lacked a clear timeline or verification measures. Questions remained regarding the summit’s efficacy in moving North Korea toward denuclearization, leading to mixed reactions.

Another summit -- held in Hanoi, Vietnam, in February 2019 -- ended abruptly without an agreement, as Trump refused to ease sanctions without North Korea committing to significant denuclearization steps. Although his bold actions attracted global attention, critics argue they ultimately fell short of delivering a meaningful shift in North Korea’s nuclear policy.

Ahn Byong-jin, a professor at the Global Academy for Future Civilizations, Kyung Hee University, recalled these summits as "dramatic shows," calling Trump the "genius of designing a drama." He opined, "You will now see something more dramatic than a Netflix series," suggesting that Trump may plan something even more spectacular regarding North Korea in his second term.

Meanwhile, Trump reentering the White House has already sparked concerns in South Korea over increased security costs and potential changes to come in the US military presence. Trump previously viewed alliances through a transactional lens under his “Make America Great Again” policy. The concern is that his second term could bring similar demands for Seoul to increase its financial contributions in return for the US military presence or renewed demands.

Ahead of the US presidential election, South Korea hastened to agree to a new Special Measures Agreement that will increase its contributions to US forces until 2030, including an 8.3 percent rise in 2026 to about 1.52 trillion won ($1.1 billion), with future increases tied to the consumer price index.

However, Trump’s previous comments referring to South Korea as a “money machine” suggest he may seek further renegotiation, possibly pushing for as much as $10 billion annually.

Trump has a history of making unreasonable demands, such as $5 billion per year -- six times the amount at the time -- at defense spending talks in 2019, when he was in his first term. This led to a protracted stalemate, and the deal was not finalized until 2021 after the Biden administration took office.

During his first term, Trump frequently raised the possibility of withdrawing or reducing US troops in South Korea, using this as leverage in costs-sharing talks. He even considered ordering the families of US troops to return home as a negotiating tactic.

Experts warn he might employ similar tactics again, which could leave South Korea bearing greater security responsibilities. Experts also say Trump’s return could signify a shift away from the long-standing joint US and South Korean objective of North Korean denuclearization.

Trump instead could focus on managing North Korea as a nuclear power, possibly lifting some sanctions in exchange for a freeze on ICBM tests. This shift could weaken the US-South Korea alliance if South Korea is left exposed to North Korea’s nuclear threat while the US prioritizes its own security, experts explained.

Moreover, Trump might consider relocating its military assets from South Korea to Japan, further straining US-South Korea relations. His first term was tempered by experienced advisers who moderated his more impulsive strategies; however, his return with MAGA loyalists could mean a shift in policy priorities in favor of his direct vision.

As Trump reenters the White House, both allies and adversaries in the region will closely observe how his administration’s unconventional diplomacy will affect East Asia. Trump’s past record shows a propensity for bold, attention-grabbing moves, yet his approach often left unresolved challenges. In his second term, the question remains whether he will build on previous milestones or create new uncertainties in US-Korean relations.