Debates in the United States about policy toward Taiwan tend to focus on the choice between strategic ambiguity and strategic clarity and how these options affect China's calculus on invading the island. The authors expand the discussion by considering how Japan, the Republic of Korea (ROK), and the Philippines would react to a range of policies the United States may choose to signal either an increase or a decrease in support to Taiwan.

To do so, the authors reviewed each ally's historical relationship with Taiwan and the contemporary relations with the United States, China, and Taiwan. They also interviewed policymakers and experts in Japan, the ROK, and the Philippines about their views on hypothetical U.S. policy changes, including potential changes in U.S. diplomatic, intelligence, military, and economic relations with Taiwan.

The authors find that Japan favors increases in many forms of U.S. diplomatic and military support to Taiwan and would adopt similar policies up to a point. The ROK and the Philippines favor the status quo and are less likely to increase support to Taiwan. All three allies oppose reductions in U.S. support to Taiwan, both because they believe it might lead to instability in the Taiwan Strait and because they would interpret reduced U.S. support to Taiwan as a signal of waning U.S. commitment to their own security. Such concerns would likely lead Japan and the ROK to try to draw the United States closer and increase defense spending. The Philippines' response would likely depend more on who is in power and China's recent behavior.