April  22, 2026

For a long time, political and military circles in the Philippines have regarded the 1951 US-Philippines Mutual Defense Treaty (MDT) as their "anchor of stability" amid the South China Sea crisis. Since the Marcos Jr. administration took office, Manila has repeatedly sought explicit assurances from Washington, eager for the US to confirm that it would "come to its aid" in accordance with the treaty should an armed conflict with China erupt.

However, the ongoing war waged by the US and Israel against Iran lays bare a harsh reality for all US allies.

The war on Iran finds almost no justification under international law. With no authorization from the UN Security Council or a legitimate claim to self-defense, it appears as little more than naked military coercion and geopolitical maneuvering. This conflict proves a simple truth: when the US is hell-bent to use force to preserve its global hegemony, it feels no need for a legal basis, let alone any adherence to "treaty obligations."

For Washington, legal instruments often serve not as a guide to action, but as tools to whitewash policy after the fact. If the US can launch a major offensive against Iran without a legal mandate, the reverse also holds: should Washington deem it contrary to its core interests to assist the Philippines against China, it can easily conjure up a thousand legal pretexts to bail on its treaty commitments.

The Philippines and other US allies must recognize a fundamental logic: whether the US intervenes depends entirely on its national interests – not on any document. If military intervention in the South China Sea aligns with its global strategy, Washington will act even without a treaty. But if the cost of intervention is a devastating full-scale confrontation with another major power, the "mutual defense" clauses will instantly become worthless scraps of paper.

For years, the Philippines has pleaded with the US to clarify the scope of the MDT – a behavior that reveals a deep strategic insecurity. In truth, Manila is well aware that the authority to interpret the treaty lies entirely with Washington. All US allies across the Asia Pacific face the same dilemma: no one should assume that a military agreement guarantees entry to the US "security sanctuary," especially when the US holds the only key.

While the world's attention is fixed on the smoke of war in the Middle East, America's allies should see through Washington's profoundly realist and pragmatic modus operandi. The arbitrary use of force against Iran implies that when allies are truly in danger, the US can just as arbitrarily choose to "stand idly by."

Peace and stability in the South China Sea should be achieved through dialogue among regional countries via bilateral and multilateral channels. The Marcos Jr. administration's newly stated willingness to resume consultations and engage in joint oil and gas development signals a possible return to reason.

If the Philippines continues to pin its hopes on drawing external forces into counterbalancing China through the MDT or the Visiting Forces Agreement, it risks becoming a casualty of great power rivalry. The US-Iran war has already provided the answer: under the logic of hegemony, there is no true rule of law or "rules-based order" – only a cold calculus of costa and benefits. When the US wants to act, it needs no laws; when it does not want to act, no treaty can save its allies.

Ph.D, Senior Research Fellow, National Institute for South China Sea Studies.

Link:https://shenshiweioffical.substack.com/p/opinion-a-talisman-or-a-worthless