Home inFocus Xi and Putin’s World Order (Summer 2023) Southeast Asian Reactions to a Taiwan Strait Crisis

Southeast Asian Reactions to a Taiwan Strait Crisis

Guermantes Lailari Summer 2023

If China moves against Taiwan or otherwise expands its borders, what happens to US alliances in Southeast Asia, what can the American military do with other allies and friends to deter Beijing and which side are Southeast Asian countries likely to take?

Positive Security Agreements

In the last decade, but mostly in the past few years, many Indo-Pacific countries have signed or are considering bilateral and multilateral security agreements. Most of the agreements are with the US and other US-allied countries. Below are highlights of these developments (the agreements are with Washington unless otherwise designated).


  • Quadrilateral Security Dialogue (Quad) (2007)
  • AUKUS: Trilateral security pact signed in 2021 between Australia, United Kingdom, and the US. In March 2023, AUKUS announced Australia would receive three to five US Virginia class nuclear attack submarines (SSNs) until Australia’s new SSNs are completed in the 2040s. Technology transfer and collaboration are other key parts of this agreement. Other countries could be added to different, less sensitive, parts of this security pact.
  • Japan-Australia Reciprocal Access Agreement (RAA) (2022)
  • Trilateral Acquisition and Cross-Servicing Agreement (ACSA) (2017) and GSMOIA (General Security of Military Information Agreement) along with Japan and the United States. These three countries announced at the 2023 Shangri-La conference that they would link their respective radar pictures for missile defense.
  • CANZUK (proposed security agreement) Australia, Canada, New Zealand, United Kingdom


  • Quad (2007)
  • GSOMIA (2002) and supplemental Industrial Security Annex (ISA) (2019)
  • Logistics Exchange Memorandum of Agreement (LEMOA) (2016)
  • Communications Compatibility & Security Agreement (COMCASA) (2018)
  • Basic Exchange and Cooperation Agreement for Geo-Spatial Intelligence cooperation (BECA) (2020).


  • GSOMIA (in negotiation)
  • Communications Interoperability and Security Memorandum of Agreement (CISMOA) (in negotiations)
  • Association of Southeast Asian Nations (ASEAN) “Our Eyes” intelligence sharing initiative (in negotiations)


  • Quad (2007)
  • GSOMIA with South Korea (2016)
  • Joint Declaration on Security Cooperation with Australia (2022)
  • Japan-Australia RAA (2022)
  • GSOMIA with Australia and US (2023)
  • Anglo-Japanese RAA (2023)
  • France-Japan defense cooperation agreement (in negotiations)
  • South Korea-Japan bilateral defense cooperation agreement (in discussions)
  • Japan-Philippines defense cooperation (in discussion)


  • US Combined Enterprise Regional Information Exchange System (CENTRIXS) in place


  • New Enhanced Defense Cooperation Agreement Sites (2023)
  • General Security of Military Information Agreement (GSOMIA) (in final negotiation)
  • Japan-Philippines defense cooperation (in discussion)
  • US CENTRIXS in place


  • Protocol of Amendment to the 1990 Memorandum of Understanding (AMOU) (2019), extended the MOU for another 15 years which enables US access to Singapore’s military facilities.

South Korea

  • GSOMIA with Japan (2016)
  • Washington Declaration (2023)
  • South Korea-Japan bilateral defense cooperation agreement (in discussion)


  • National Defense Authorization Act (NDAA) for Fiscal Year 2023 which includes the Taiwan Enhanced Resilience Act (TERA)

Thailand (most recent agreements)

  • CISMOA (2014)
  • Acquisition & Cross-Servicing Agreements (ACSA) (2014)


In 2018, Vietnam participated for the first time in the Rim of the Pacific (RIMPAC) military biennial exercise, after sending observers in 2012 and 2016.”

In 2020, the EU-Vietnam Framework Participation Agreement (FPA) will “facilitate Vietnam’s participation in and contribution to the EU’s Common Security and Defense Policy (CSDP) missions and operations.”

China’s Alliances

Besides the formal agreement Sino-North Korean Mutual Aid and Cooperation Friendship Treaty (1961), China has no publicly declared security agreement except for the Solomon Islands-China Security Pact (2022). Other Southeast Asian countries appear to have secret agreements with China, one example of this is between China and Cambodia, probably signed in 2019, regarding a naval facility being built at Ream naval base for the People’s Liberation Army (PLA) Navy. Clearly, Pakistan is an ally of China without a public declaration.

Myanmar is another Southeast Asian country that likely has a secret security agreement, given that the Chinese Communist Party (CCP) supported the military coup and is building bases and has intelligence collection sites there.

Laos is also a close Chinese partner with most of its economic activity related to the China’s Belt and Road Initiative. Laos will most likely stay neutral in a Taiwan crisis or support China.

Combined Military Planning, Operations, Training, and Exercises

In a dystopian future, China intends to encircle Taiwan, invade, and block the US military from providing assistance when war breaks out. What practical exercises and preparations can Taiwan and US militaries undertake?

First, US-Taiwan militaries will be increasing their combined training, exercises, and operations. The most important step is to try to deter China from believing it can conquer Taiwan. Already, the number of US advisors training Taiwanese forces has increased dramatically while Taiwan Army units—believed to be battalion-sized—are training in the US with US Army National Guard units. The is a drastic shift from decades-long American shunning of the Taiwan military owing to fears of Beijing’s reaction.

The second step is to ensure that should deterrence fail, Taiwan, the US and other countries are prepared to prevent the PLA from permanently controlling Taiwan, its islands, and its territorial waters and exclusive economic zone (EEZ).

Prepositioning Weapons

One important way to push back against China for its ongoing aggression against Taiwan is to preposition weapons in Taiwan and its islands for both US and Taiwanese use. The US can add to Taiwan’s stockpile of key weapons and preposition weapons for its own use in case America ends up defending Taiwan with boots on the ground. Similarly, the US could also preposition weapons and supplies in nearby countries such as Japan, South Korea, Philippines, Palau, and even Australia. The movement of forces or rotating forces continuously to and from these countries will help deter China and enhance the US military’s lethal capabilities in the region.

With respect to deterring China, here are additional actions that the US and Taiwan can undertake (and in some cases already have):

  • Enhanced military training, exercises, and operational planning to deter the CCP from ordering an invasion, blockade, missile strikes or other aggressive actions.
  • The US government has approved a loan of up to $2 billion for Taiwan to buy weapons from US companies.
  • In addition to the loan, the Biden administration approved a $619 million arms sale to Taiwan in March 2023 that will include the following weapon systems to increase the lethality and survivability of Taiwan’s F-16V aircraft against radars and adversary aircraft: 100 AGM-88B High-Speed Anti-Radiation Missiles; 23 HARM training missiles; 200 AIM-120C-8 Advanced Medium Range Air-to-Air Missiles; 4 AIM-120C-8 AMRAAM Guidance Sections; and 26 LAU-129 multi-purpose launchers.
  • The US government needs to apply as much pressure on industry to expedite delivery of the more than $19 billion in backlogged weapons Taiwan has already purchased. If these are not delivered soon, the president should consider taking stocks from the US inventory or changing delivery priorities.
  • In response to pressure from Congress and Taiwan, in May, President Biden approved via his Presidential Drawdown Authority, sending part of a $500 million purchase of FIM-92 Stinger air defense missiles to Taiwan.

Second, because of the NDAA and its specific requests to support Taiwan, the island should be able to plan, conduct, train, and exercise for combined operations with the US and other allies in the following areas (not a comprehensive list):

During peacetime:

  • Freedom of Navigation operations with navy vessels and military aircraft.
  • Humanitarian Assistance and Disaster Relief (HADR).
  • Counter-smuggling operations.
  • Counter illegal unreported and unregulated (IUU) fishing operations.
  • Counter CCP grey zone operations.
  • Combined military exercises.

During peacetime, higher levels of tension, and wartime:

  • Counter blockade operations.
  • Counter invasion operations.
  • Counter missile strikes.
  • Conducting special operations.
  • Conducting all-domain conventional operations.
  • Conducting irregular warfare.
  • Countering media, psychological, and legal warfare.
  • Command and control of friendly forces.
  • Intelligence operations.

Third, the NDAA specifically encourages the US Department of Defense to allow Taiwan’s military to participate in the 2024 Rim of the Pacific (RIMPAC) exercise. This invitation could include, at a minimum, allowing Taiwanese military personnel as observers on US Navy ships and at command-and-control locations in or around Hawaii and vice versa to familiarize each side with standard operational and emergency procedures. At the maximum, the Taiwanese military’s joint force (Navy, Army, and Air Force) could participate in pre-planning events and execution with all other participating RIMPAC countries as appropriate next year (2024).

Finally, encouraging Taiwanese naval ships, aircraft, and army to visit Guam, Hawaii, and other US bases in the Indo-Pacific and US forces to visit Taiwan frequently also would enhance combined training, exercises, planning, and operations.

Southeast Asian Reactions to a Taiwan Crisis

Southeast Asia consists of 11 countries: Brunei, Myanmar, Cambodia, Timor-Leste, Indonesia, Laos, Malaysia, the Philippines, Singapore, Thailand, and Vietnam.

Most Likely to Support Taiwan

Although many countries would prefer to stay out of the fight, countries such as Australia, Japan, South Korea, Philippines, Singapore (possibly neutral), and Thailand (the last three are Southeast Asian countries) will most likely participate at some level in a future conflict due to their close security relationships with Washington. Furthermore, the US has military forces deployed in these countries and the bases they are assigned to will provide logistics support at a minimum. These bases also could be used to conduct strikes against PLA forces attempting to coerce Taiwan.

Of the three Southeast Asian countries above, the Philippines has a stronger relationship with the US and Taiwan than do Thailand and Singapore.

Thailand might be the one US allied country that does not participate militarily due to the PRC’s highly successful political warfare conducted within the kingdom and its uncomfortable proximity to China’s secret allies: Myanmar, Laos, and Cambodia.

Singapore’s position supporting Washington and Taipei also could be wobbly now that the island state is, for the first time, ruled by a pro-PRC administration. In addition, some experts have noted that Singapore always has played both sides for its own advantage and could shift to China because of its small geographic size (275 square miles or smaller than Rhode Island), population of 5.4 million (second densest city in the world), 76 percent of its population is ethnic Chinese, and Singapore is challenged by the CCP’s political warfare activities.

The remaining Southeast Asian countries that have territorial and economic exclusion zone (EEZ) interests in what is called the “South China Sea” could resist PLA encroachment. These are Brunei, Cambodia, Indonesia, Malaysia, and Vietnam. Even then, they are unlikely to go all-in and support the US and its partners. For example, the Malay government might try to negotiate a bilateral settlement with China if it believed that this was its best option.

Very Likely Supporters

Since China most likely will not stop its expansionism after taking Taiwan since Taiwan is part of the CCP’s so-called “10-dash line,” the following countries will most likely work together to protect their respective national exclusive economic zones from Chinese aggression: Brunei, Indonesia, Malaysia (maybe), Philippines, Singapore (maybe), and Vietnam.

Southeast Asian Countries’ Alliances (Image: Guermantes Lailari)

Although Vietnam is ruled by a communist party, Vietnam has been the victim of numerous PLA attacks along its 800 mile common land border (1979) and its SEAS islands (1974, 1988, 1994, 2012), and PLA harassment of Vietnamese fishing boats and its oil and gas exploration efforts. The Vietnamese are pugnacious, but there are limits to what these countries can do militarily against the PLA either individually or collectively.

Least Likely Supporters

Mainly due to secret security agreements or heavy economic leverage, the following countries would not support Taiwan and probably not back the US and partners in a crisis: Myanmar, Cambodia, Laos, and possibly Timor-Leste. These countries could end up being allies of China as hostilities developed and they are forced to choose sides.

The CCP could use these secret allied countries as staging areas for the PLA to attack Thailand or against Southeast Asian nations protecting their EEZs and thereby attempt to draw US military and its allies away from PLA actions against Taiwan—classic divide and conquer strategies.

Can Taiwan and the US Cooperate?

There are several areas in which Taiwan, the US, and other allied countries could collaborate in the region. These include:

Conduct contingency planning for possible Humanitarian Assistance and Disaster Relief (HADR) operations as well as planning for contingencies during heightened levels of conflict/tension.

Provide for logistics support (supplies), emergency operating locations, and repair facilities for US and allied military aircraft and ships.

Assist in documenting United Nations Convention on the Law of the Sea (UNCLOS) violations in support of SEAS countries such as Philippines, Indonesia, Brunei, Vietnam, Malaysia, Singapore, and other friendly interested countries such as South Korea, Japan, Australia, and European countries.

Allow US military personnel to visit Taiwan’s SEAS islands (Itu Aba Island / Taiping Island and Pratas Island / Dongsha Island – currently designated a national nature preserve). They could discuss reciprocal support during operations, exercises, training, and during wartime.

Conduct bilateral and multilateral planning, training, exercises, and operations in Southeast Asia.

Image: CSIS

SEAS Allied Air Bases

Should China become more aggressive, the Southeast Asian countries could form an alliance with other concerned states and use their current island bases to support military operations as well as using their home country bases. The following countries have militarized their islands:

  • Taiwan: Itu Aba Island (Spratly)
  • Vietnam: Spratly Island/Đảo Trường Sa
  • Philippines: Thitu Island (Spratly)
  • Malaysia: Swallow Reef (southern Spratly islands)
  • Indonesia: Natuna Besar Island (not in the Spratly islands)

See the comparison of runway sizes of some of the islands compared to one of four of China’s illegally occupied islands—Fiery Cross Reef located in the Spratly Islands area.

Parts of Pratas Island are currently designated a Taiwan national nature preserve (two coral reefs, North Vereker Bank and South Vereker Bank) and many environmentalists and perhaps some pro-China politicians in Taiwan do not want to militarize it. The main island already has a 1,550-meter concrete runway (see island photo). However, as China becomes more assertive in its claims inside of the so-called “ten-dash line,” Taiwan should re-consider making Pratas Island military friendly.

Pratas (Dongsha) Island

Clearly, if the PLA takes Taiwan or even its islands, the it will militarize Pratas Island giving it a strategic location to better control the southern entrance of the Taiwan Strait and as an additional location from which to conduct military operations southward against the Philippines or even against Taiwan.

Pratas (Dongsha) Island. (Photo: Taiwan Water Resources Bureau)


Just as today’s Italy does not claim the territory of the Roman Empire, and Turkey does not claim the Ottoman Empire’s land, the Chinese Communist Party has no right or claim to Taiwan, Southeast Asian seas, the Japanese Senkakus or the Ryukyu Islands, nor parts of India, or even parts of Russia—note recent attempts to rename Russian cities with Chinese names, and territories of the other nations that surround it. Furthermore, the CCP currently illegally occupies Tibet, East Turkestan, parts of Mongolia, land taken during China’s 1979 invasion of Vietnam, and other areas.

As noted earlier, Thailand and Singapore might try to stay neutral despite their defense agreements with the US.

On the other hand, based on the increased number of interlocking defense agreements between Southeast Asian countries and to outside European countries, we are seeing the beginning of a new alliance structure that will greatly complicate China’s plans for Asian domination. For example, the “four foundational” agreements that India and the US have signed provide the legal, diplomatic, and defense infrastructure for them to easily declare an alliance when both sides determine the need. This formula is in progress with many other countries in the region.

Taiwan, the US, the Southeast Asian countries, and other allies can greatly enhance their military options in deterring China’s PLA aggression against Taiwan and the SEAS. The United States, Taiwan, and their allies should begin the process now to agree to all four foundational agreements to ensure coordination, deconfliction, mutual support, training, exercises, and planning to deter China. Should deterrence fail and this advice is heeded, these countries will be more ready to confront China and force it to pay dearly for its colonial expansionism.

Guermantes Lailari is a visiting Scholar at National Chengchi University and a retired USAF Foreign Area Officer.