Asian allies on edge: Japan and South Korea brace for uncertainty in Trump’s second term

The trilateral cooperation between Japan, South Korea, and the United States is showing cracks. Already fragile under the previous  US President Joe Biden, the alliance faces further strain under President Donald Trump, whose role as a mediator between historical antagonists Japan and South Korea is seen as unlikely by both these American allies and the international community.

During his first term from 2017-21, Trump favoured direct, face-to-face diplomacy over multilateral cooperation. His short-term policy approach and lack of diplomatic weight raise concerns about the future of this partnership. Trump sees alliances primarily as tools to serve US interests, prioritising his administration’s “America First” policy over broader regional security in the Indo-Pacific.

Political shifts weaken trilateral cooperation

Recent political changes in all three nations have the potential to weaken trilateral cooperation further. Trump’s election as US President in November 2024 has unsettled Indo-Pacific allies. In Japan, Prime Minister Shigeru Ishiba leads a weakened government following a scandal involving the Liberal Party after the October 2024 parliamentary elections.

In South Korea, conservative, pro-US President Yoon Suk Yeol faces impeachment after being suspended for declaring martial law. Unlike his predecessor, Moon Jae-in, Yoon sought to strengthen ties with both the US and Japan. However, South Korea’s current turmoil could disrupt trilateral collaboration.

The importance of stability

Both Japan and the Korean Peninsula hold critical geostrategic significance in East Asia, making their internal stability a key concern. Japan remains wary of South Korea’s political situation, often referring to the peninsula as “a dagger pointed at the heart of Japan”, a phrase attributed to Prussian adviser Jakob Meckel, who worked for the Meiji government.

Historical tensions continue to heighten regional and international friction. These tensions weaken the coalition against China’s growing influence and undermine Tokyo’s foreign policy strategy. The persistent discord between Japan and South Korea – both key US democratic allies – poses a challenge for Washington.

Internal stability in Japan and South Korea remains vital for the US, which maintains numerous military bases and troops in both nations. However, one issue could strain the trilateral alliance further: disagreements over shared military costs due to rising defence spending demands.

North Korea and China add to security concerns

Such tensions could prove detrimental at a critical time. North Korea has accelerated its nuclear and missile programmes, developing advanced weapons that threaten regional and global stability. Meanwhile, China is expanding its influence through aggressive actions in the South and East China Seas, economic coercion, and an increased military presence.

For South Korea, US support is now more crucial than ever. Seoul remains wary of Trump’s potential foreign policy moves, particularly regarding North Korea. Trump has already planned to meet with Kim Jong Un, as he did three times during his first presidency – without South Korean officials present. This has heightened concerns in Seoul about being sidelined in critical diplomatic discussions.

Wounds from the past

The primary source of friction between Japan and South Korea lies in Japan’s colonial rule over the Korean Peninsula, particularly the atrocities committed by Japanese forces during World War II. Thousands of “comfort women” were forced into sexual slavery to “boost the morale” of invading troops.

After decades of silence, survivors came forward in the 1990s, demanding recognition and accountability from Tokyo. While South Korea shed light on these abuses, Japan’s political stance shifted under Prime Minister Shinzo Abe, who took office in 2006 and remained influential until his assassination in 2022. His administration adopted a more rigid position on the comfort women issue, further straining relations. The Japanese government continues to deny acknowledging crimes committed by its military forces during the Second World War.

China’s rising shadow weakens trilateral unity

China remains a shared concern for Japan, South Korea, and the US. Yet, trilateral cooperation remains weak, largely due to China’s economic significance to all three nations. Japan has long pursued strategies to counter China’s regional dominance, while South Korea, particularly under Moon Jae-in, maintained a “strategic ambiguity” approach. However, under Yoon, South Korea has aligned more closely with the Indo-Pacific Strategy, a framework backed by Japan and the US to curb Beijing’s influence.

Yoon’s policy shift has strengthened South Korea’s position as a more reliable partner for Japan, creating new opportunities for dialogue. However, Trump appears unwilling to seize these opportunities or position himself as a facilitator of diplomatic engagement.

Regardless of potential US mediation, this developing dialogue between South Korea and Japan could mark a positive step for trilateral cooperation, particularly in countering China’s influence.

Prospects with Trump in power 

Thanks to more defined political strategies from Japan, South Korea, and the Biden administration, a new phase of trilateral cooperation began at the Camp David Summit in summer 2023.

Despite challenges, security and defence officials from the three nations held multiple meetings across all government levels over the past two years. They also developed multi-domain military exercises and enhanced economic, financial, technological, and civilian cooperation.

However, concerns persist that Trump’s unpredictable, transactional diplomacy could undermine these efforts. His isolationist stance, reluctance towards multilateral dialogue, and limited willingness to cooperate make it unlikely that he will engage in East Asia to support allies, as this could risk military escalation.

Trump’s focus in East Asia is expected to centre on North Korea and China rather than maintaining alliances. To ensure stability, he would need to adopt a more strategic, less transactional approach to partnerships – one that reaffirms collective defence commitments and maintains clear communication.

The need for strong alliances

The trilateral alliance between the US, Japan, and South Korea is critical for regional stability. In a rapidly evolving security landscape, the success of this partnership is essential for maintaining peace and countering threats from China, North Korea, and Russia. Strong democratic values, robust cooperation, and consistent diplomacy are necessary to counter these threats effectively.

Demonstrating unity, US Secretary of State Marco Rubio, Japanese Foreign Minister Iwaya Takeshi, and South Korean Foreign Minister Cho Tae-yul met on the sidelines of the Munich Security Conference on February 15, 2025, to reaffirm their commitment to trilateral cooperation. The need for strong alliances is more pressing than ever. However, uncertainty surrounding Trump’s leadership continues to cast doubt over the future of this critical partnership.

Camilla Cavarape holds a Master’s degree in International Relations from the Catholic University of Sacred Heart, in Milan. She is currently a PhD candidate in Development Studies at the University of Lisbon. Her research focuses on social, cultural, and political transformations in Asia and Latin America, with a particular emphasis on Brazil, where she carried out fieldwork in her capacity as a researcher.

Originally published under Creative Commons by 360info™.

(Cover Photo: Japan-South Korea summit meeting in 2024, available at https://commons.wikimedia.org/wiki/File:Japan-South_Korea_summit_meeting_(2024).jpg Credits CC BY 4.0)