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Guest Column

One of American President Donald Trump's longstanding policy stances, which he has held since at least 1987, is that US’ allies ought to pay their ‘fair share’ for the security assurances they receive. How will Trump’s perception of allies as free riders who tie US hands affect Southeast Asia’s geostrategic positioning under his second term? This essay investigates ways in which Southeast Asian countries can tackle uncertainties stemming from the risk of US retrenchment. It argues that if Trump follows its transactional and isolationist foreign policy approach, US partners in Southeast Asia are likely to mitigate the effects of US retrenchment. This is because there are limits to how much the US can retrench, and even if the US withdraws some of its security commitments and Southeast Asia moves closer to China, the region still maintains the ability to constrain China’s assertiveness.

What Trump 2.0 Means for Global Order and Southeast Asia

A key implication of Trump 2.0 is that the old hegemon–the US–is retreating and the rising global power–China–is not yet ready to take over, which leads to a paradigm shift of having no clearly defined leader in world politics. How exactly this will play out for Southeast Asia will depend on the interplay of a number of factors. In his first term, Trump had showed apathy towards Southeast Asia. However, drawing on his experiences from the first term, he is likely to focus more confidently on countering China, which will inevitably impact Southeast Asia as the region seeks to maintain a balance between the US and China. Furthermore, Marco Rubio, appointed as secretary of state, Mike Waltz, named as national-security adviser, and Peter Hegseth, appointed as defence secretary, are all China hawks. These factors combined with Trump’s contempt for alliances, point towards heightened US-China tensions, potential renegotiation of alliance terms, and a greater emphasis on countering Chinese influence. US engagement in the Southeast Asian region may also be shaped by several institutions including Congress, the State Department, and the US Indo-Pacific Command.

Potential Security Scenarios for Southeast Asia

Taking the above factors into consideration, there are several plausible scenarios for Southeast Asia, ranging from US neglect to being caught up in a China escalation as a worst-case outcome.

Scenario 1: Partial US Retrenchment amidst Restructured Alliances

While Southeast Asia is not a priority for Trump, the region's strategic importance will still necessitate some level of engagement to protect trade routes and US economic interests in the region. A complete withdrawal would alienate regional allies and allow China to gain greater influence over critical areas of global commerce and security. Therefore, one possible outcome is that Trump’s administration may focus on reinforcing existing alliances while simultaneously reducing overall military commitments. This could manifest through the US placing greater emphasis on joint military exercises with key US Asia-Pacific allies such as Australia and Japan, while reducing rotational deployments and military presence in Southeast Asia.

Scenario 2: A shift Towards Bilateral Engagement

A second scenario involves a pivot towards bilateral engagement where Trump negotiates individual agreements with the Southeast Asian nations based on their strategic importance to US interests. This approach could lead to tailored security arrangements that would ensure that key players with maritime claims in the South China Sea like Vietnam and the Philippines remain aligned with US objectives against China. The other Southeast Asian countries would face two options: either bear the costs to maintain US security commitments or accept that such commitments might become conditional on their willingness to help the US isolate or confront China. Bilateral arrangements, however, could lead to fragmentation within ASEAN as member states may prioritise and pursue individual deals rather than collective security arrangements.

Scenario 3: Power Vacuum Filled by Middle Powers or China

If the US significantly retrenches from Southeast Asia, middle powers like Japan, in collaboration with South Korea or the European Union (EU), could attempt to fill the resulting vacuum. Alternatively, China might seize this opportunity to expand its influence further in Southeast Asia through economic investments and military partnerships, potentially driving US partners closer to China. During a potential US-China escalation, if US pressure and demands to Southeast Asia become too onerous, this strategy could backfire. Dependence on the US for security could become too costly or uncertain, jeopardising Southeast Asian countries’ relations with China. As a result, these countries might reject Trump’s terms and increasingly look for alternative security partners.

Available Security Strategies for Southeast Asian Countries

Given the listed scenarios, how can Southeast Asia navigate a potential US retrenchment? Acknowledged for their pragmatic foreign policies and hedging acumen, Southeast Asian countries can use a combination of strategic options.

Strategy 1: Strengthening Regional Cooperation and Cohesion

Southeast Asian countries can enhance cooperation through ASEAN frameworks to discuss security concerns and present a unified front against external pressures thus supporting the region’s strategic autonomy and regional stability amongst geopolitical shifts. This would bolster their negotiating power with both the US and China—-strengthening ASEAN centrality. Enhancing ASEAN unity and consensus-building mechanisms is critical, because it can prevent US-China tensions from spilling over further into Southeast Asia and help maintain China’s restraint in the South China Sea. As the 2025 ASEAN chair, Malaysia will therefore have a daunting task of upholding ASEAN’s cohesiveness.

Strategy 2: Diversifying International Partnerships

ASEAN should strive to establish stronger partnerships with like-minded powers, such as Japan, South Korea, India, Australia, and the EU. Leveraging ASEAN-led mechanisms can provide a useful platform for fostering multilateral dialogue and collaboration. At the same time, deeper security cooperation can also be accomplished through frameworks such as the Quad Plus to align interests, achieve shared objectives, and preserve the rules-based order in the Indo-Pacific. Southeast Asia thus does not have to only rely on traditional alliances but can also use a diversified diplomatic approach capitalising on both multilateral and minilateral cooperation to reinforce its security posture.

Strategy 3: Improving Defence Capabilities

Finally, Southeast Asian countries can boost their resilience by modernising their armed forces and building their domestic production capabilities. They can also seek technology transfers from partners such as Japan or South Korea. Beyond hardware improvements, the region should increase capacity-building initiatives to strengthen maritime domain awareness and its operational ability to respond to future security challenges.

To conclude, Southeast Asian countries can effectively navigate the uncertainties of Trump’s potential retrenchment by adopting proactive strategies to safeguard their security interests. In particular, Trump’s second term will be a litmus test for ASEAN-led multilateralism. However, US retrenchment poses a double-edged sword, as regaining lost trust from such a strategic region will not be easy.

Barbora Valockova is a Postdoctoral Fellow at the Centre on Asia and Globalisation (CAG) at the Lee Kuan Yew School of Public Policy, National University of Singapore.

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The views expressed in the article are solely those of the author(s) and do not necessarily reflect the position or policy of the Lee Kuan Yew School of Public Policy or the National University of Singapore.

Image Credit: Flickr/U.S. Secretary of Defense

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