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By Bonnie Yushih Liao 廖雨詩
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For Taiwan, the ongoing US and Israeli strikes on Iranian targets are a warning signal: When a major power stretches the boundaries of self-defense, smaller states feel the tremors first.
Taiwan’s security rests on two pillars: US deterrence and the credibility of international law. The first deters coercion from China. The second legitimizes Taiwan’s place in the international community. One is material. The other is moral. Both are indispensable.
Under the UN Charter, force is lawful only in response to an armed attack or with UN Security Council authorization. Even pre-emptive self-defense — long debated — requires a demonstrably imminent threat.
Preventive war seeks to eliminate a potential danger before it materializes.
That distinction is the line separating order from opportunism.
Several respected international law scholars have argued that the threshold of imminence was not met in Iran’s case. There was no publicly available evidence that Iran was on the verge of launching an attack, nor that it possessed operational nuclear weapons ready for use.
If the rationale rests on stopping a future capability rather than countering an imminent assault, the justification shifts from defensive necessity to strategic choice.
Strategic choice is precisely what the US condemned elsewhere.
When Russian President Vladimir Putin invoked NATO expansion and future security risks to justify the invasion of Ukraine, Washington rejected the logic outright.
Hypothetical threats do not authorize war, it insisted.
International order cannot survive if states attack whenever they perceive a possible future disadvantage.
If that principle bends, its authority weakens.
Beijing has long described Taiwan’s democratic consolidation, its military modernization and growing security ties with Washington as destabilizing trends.
The language of “future threat” already exists in Chinese strategic discourse. If preventive force becomes normalized in practice, that language gains rhetorical ammunition.
Precedent shapes perception. Perception shapes risk.
International norms survive not because they are universally obeyed, but because they are consistently defended.
When leading democracies carve out exceptions, the shield surrounding smaller democracies thins.
Taiwan’s leaders cannot afford distance from Washington; US support remains the cornerstone of deterrence.
However, uncritical endorsement of legally contested action risks undermining Taiwan’s own long-standing argument that power must be constrained by rules.
At home, the government must ensure that the public is acutely aware of cross-strait danger, while navigating partisan scrutiny.
Abroad, it must demonstrate reliability as an ally without surrendering the normative ground that distinguishes Taiwan from the authoritarian model it resists.
It is a narrow corridor — alliance solidarity on one side, legal consistency on the other.
Deterrence without legitimacy invites suspicion. Legitimacy without deterrence invites pressure. Taiwan has no luxury of choosing between the two.
The deeper danger lies in normalization.
Once preventive war becomes routine rather than exceptional, the vocabulary of “anticipated threat” becomes available to every major power.
In East Asia, that vocabulary carries explosive implications.
Taiwan’s security has always depended not only on military balance, but on the integrity of the rules-based order. When those rules appear selective, their deterrent value erodes.
When the ground shifts beneath international law, Taiwan stands closer to the fault line than most.
Bonnie Yushih Liao is an assistant professor in Tamkang University’s Department of Diplomacy and International Relations.
