Prior to 1992, Philippine-U.S. security relations were framed by several bilateral defense arrangements. The two countries became formal allies in 1951 upon signing the Philippines-U.S. Mutual Defense Treaty. Both countries also became members of the Southeast Asia Treaty Organization in 1956. However, the most important of these bilateral defense arrangements predated the collective defense treaties binding the two countries: the 1947 Philippines-U.S. Military Bases Agreement, which facilitated the hosting of major American naval and air facilities in Philippine territory. The U.S. military bases in the Philippines, including the Subic Bay Naval Base and Clark Air Base, extended vital logistical support to American forward-deployed forces operating in Southeast Asia, the Indian Ocean and even in the Persian Gulf during the Cold War. Furthermore, U.S. air and naval assets acted as de facto armed forces against external threats to the Philippines, since the Philippine military was primarily involved in internal security operations.
In September 1991, the Philippine Senate failed to ratify the Philippine-American Cooperation and Friendship Treaty of 1991 (PACT). PACT provided the legal basis for extending the stay of the U.S. military facilities on Philippine territory beyond 1992. Motivated either by simple anti-Americanism or disgust over the low base-related economic and military compensation, the majority of the senators voted down the treaty. With the withdrawal of these American military facilities from the country in 1992, the alliance assumed a form different from the previous configuration. Philippine-U.S security relations became dormant as the Philippines focused its attention on the Association of Southeast Asian Nations (ASEAN). Meanwhile, the U.S shifted its strategic priorities away from Southeast Asia to Northeast Asia.
Starting in 2001, the U.S. global war on terror, and later the tension in U.S.-China relations after 2008, helped restore the U.S.-Philippines strategic partnership. Security relations were revitalized, and the alliance achieved two political and strategic objectives. First, Manila received U.S. support for the Philippine government’s counterterrorism and counterinsurgency campaign in the country’s south. Second, Washington deepened its alliance with Manila, not only to neutralize terrorist groups, but also to counter Beijing’s political and economic influence in the country. The U.S. now regularly extends technical training and defense assistance to the armed forces of the Philippines (AFP) to firm up the U.S.-Philippines security partnership in the face of growing Chinese military power and assertiveness in the South China Sea.