South Korea’s New Leader Is Facing an Old Problem

South Korea’s new president has only been in the job a few days, but he already risks repeating past mistakes. The moment calls for a rethink in the US ally’s defense posture. 

It’s unclear if Lee Jae-myung is up to the task — or whether he will cling to failed strategies to deal with nuclear-armed North Korea. The left-leaning leader secured victory on Tuesday, and healing a divided nation will be his top priority. The country is still reeling from the fallout of a brief period of martial law imposed by his predecessor, the now-impeached Yoon Suk Yeol. 

The economy is entangled in President Donald Trump’s trade war, and faces a 25% across-the-board levy due to go into effect in July unless a deal is struck. Lee’s first day in office was marked by Trump’s move to raise import taxes on steel and aluminum to 50% from 25%. Bloomberg Intelligence warns the domestic steel industry could be severely hurt, as America accounted for over 10% of its 2024 exports.

Still, even with these pressing economic concerns, security is focusing minds both domestically and globally. North Korea is acting with more confidence thanks to its expanding ties with Russia. It shares a fraught relationship with its other partner, China, which is no longer as close, but Beijing’s expansionist agenda is worrying the region and the West. Seoul cannot afford to create any potential opening for Kim Jong Un to destabilize the peninsula further. 

His regime is accelerating its nuclear weapons and ballistic missiles program at a rapid pace. Current estimates suggest Pyongyang has enough fissile material to build up to 90 nuclear warheads, the Atlantic Council notes. Kim has placed increasing importance on nuclear weapons development as a way to overcome the South in any eventual war.

Lee is acutely aware of the challenges. During his inaugural speech on Wednesday, he said he planned to counter the threats through “strong deterrence” anchored in the South Korea-US alliance, while also pursuing a willingness to “open lines of communication” with Pyongyang. Notably silent in response to Lee’s remarks, the North had become increasingly hostile in the Yoon years, rejecting dialogue and threatening to use its atomic weapons. 

Up until now, Seoul has relied on Washington for its security, but that partnership is under pressure. Trump has pushed US allies to step up military spending in return for deploying American troops in conflict zones. In October, he said South Korea would pay billions of dollars more every year if he were in the White House and called the long-time ally a “money machine.”

The White House has been ambiguous about whether the US military will continue to offer protection as it has in the past. US troops have been based in the South since the 1953 armistice that formally ended the Korean War, with the aim of deterring Pyongyang. Reports of a potential withdrawal of a brigade from the peninsula is making Seoul nervous. 

The US Department of Defense has dismissed concerns, but others have noted the issue is under serious consideration at the Pentagon, US Forces Korea, and Indo-Pacific Command. Adding to the anxiety, Secretary of Defense Pete Hegseth skipped Seoul on his recent trips to the region. Indeed, during a speech at the International Institute for Strategic Studies Shangri-La Dialogue, a premier regional security forum in Singapore last weekend, South Korea was barely mentioned. 

Trump likes to point to his relationship with Kim as the reason why he thinks he can bring peace to the Koreas. In March, he said he plans to reach out to the North Korean leader “at some point.” But Lee would be wise to remember what happened during the US president’s first term, when closer ties between Trump and Kim led to the scaling down of some major military drills. 

Lee has an opportunity to mitigate the risks of an unpredictable White House by building on the relationship with Japan, despite historic tensions. A united front between Seoul and Tokyo would enhance regional stability and present a stronger deterrent against North Korea. Japan has welcomed the new leader’s overtures, with Prime Minister Shigeru Ishiba proposing a face-to-face summit soon. 

Investing more in homegrown missile defense would also be prudent. In January, Seoul began the development of an interceptor system after Israel’s Iron Dome, aimed at shielding civilians and military assets from potential strikes by the North. It’s expected to come into operation in 2028. Domestic defense companies are also ramping up investment in AI-powered military technologies. Staying ahead in this arena will be crucial to curbing Kim’s nuclear ambitions.

Finally, public opinion will likely compel Lee to seriously consider the case for nuclear armament, as a way to develop autonomous self-defense and reduce dependence on the US. With North Korea’s nuclear weapons program now widely seen as irreversible, sentiment has shifted dramatically. Polls consistently show that over 70% of citizens support developing their own nuclear deterrent. 

South Korea’s new president will need to balance their desires with the alliance with Washington. The Trump administration’s unpredictability is forcing Lee to take decisive action to protect his citizens, with or without America’s lead. 

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This column reflects the personal views of the author and does not necessarily reflect the opinion of the editorial board or Bloomberg LP and its owners.

Karishma Vaswani is a Bloomberg Opinion columnist covering Asia politics with a special focus on China. Previously, she was the BBC’s lead Asia presenter and worked for the BBC across Asia and South Asia for two decades.

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