Mutual Defense Treaty (United States–Philippines)

The Mutual Defense Treaty between the United States of America and the Republic of the Philippines is a treaty signed on August 30, 1951, in Washington, D.C., committing both nations to support each other if either the Philippines or the United States is attacked by an external party. The treaty stipulates that an armed attack on either country in the Pacific area would be dangerous to its own peace and safety and that each would act to meet the common dangers in accordance with its constitutional processes.

The treaty consists of eight articles and is indefinite in duration. It outlines a mutual commitment to collective self-defense, focusing on addressing external armed attacks. The geographical scope of the treaty initially covered attacks on metropolitan territory, island territories under jurisdiction, or on armed forces, public vessels, or aircraft in the Pacific. However, interpretations of the treaty's application to disputed territories in the South China Sea, specifically concerning the Philippines' claims, have been debated and adjusted over time through subsequent agreements and statements by both countries.

Key aspects of the treaty include:

• Mutual Defense Obligation: The central provision requiring each nation to come to the aid of the other in the event of an armed attack in the Pacific.
• Constitutional Processes: Any action taken under the treaty is subject to each nation's constitutional requirements.
• Collective Self-Defense: The treaty is rooted in the principle of collective self-defense as recognized under Article 51 of the United Nations Charter.
• Consultation: The treaty mandates consultation between the two countries in the event of an armed attack or threat thereof.

The Mutual Defense Treaty has been a cornerstone of the U.S.-Philippine alliance for decades. It has been invoked and reaffirmed on numerous occasions, and it continues to shape the security relationship between the two countries. Interpretations of the treaty and its practical application have evolved in response to changing geopolitical circumstances and security challenges in the Asia-Pacific region. Recent interpretations have clarified the treaty's applicability to attacks on Philippine vessels or aircraft in the South China Sea, although specific circumstances and responses remain subject to ongoing discussions and policy decisions.