The recent visit of U.S. secretary of state Michael Pompeo to Manila settled a long-standing concern in the Philippines over U.S. commitment to Philippine security in the South China Sea. In a press briefing with Philippine secretary of foreign affairs Teodoro Locsin, Jr., Pompeo unequivocally articulated what the Obama administration never publicly did: “As the South China Sea is part of the Pacific, any armed attack on Philippine forces, aircraft or public vessels in the South China Sea will trigger mutual defense obligations under Article 4 of the  Mutual Defense Treaty [MDT].”
Article 4 expressly provides that “an armed attack in the Pacific Area on either of the Parties” would require each nation to “act to meet the common dangers in accordance with its constitutional processes.” In reference to this, Article 5 of the MDT clarifies: “an armed attack on either of the Parties is deemed to include… its armed forces, public vessels or aircraft,” as well as metropolitan and island territories.
Pompeo’s policy statement should not come as a surprise; the U.S. Navy’s routine freedom of navigation operations (FONOPS) in the South China Sea and passages through the Taiwan Strait underscore a renewed effort to demonstrate U.S. security concerns in the newly-dubbed INDOPACOM, or Indo-Pacific Command, area of responsibility. But while Pompeo’s reassurance on the MDT’s geographic scope may assuage Philippine anxiety over one aspect of the treaty, the agreement is more complicated than that, and some in Manila worry more over just what circumstances would persuade Washington to uphold the treaty—or demand that it be upheld.
Major Issues for Review
Despite Pompeo’s strategic clarity and its reception by Secretary Locsin, Philippine secretary of national defense Delfin Lorenzana held fast to his call for a review of the MDT. In December 2018, Lorenzana surprised complacent security watchers in Washington when he announced that the MDT ought to be reviewed to determine whether it should be “maintained,” “improved,” or “scrapped.”
Secretary Lorenzana saw that the Philippines benefits from its alliance with the U.S. through mechanisms such as the Visiting Forces Agreement and the Enhanced Defense Cooperation Agreement (EDCA). However, Lorenzana also recognized the ambivalence in the operationalization of the retaliatory clause in Article 4 of the MDT, particularly the wording that each Party would “[a]ct… in accordance with its constitutional processes.” As early as 1982, then-president Ferdinand Marcos had contended that if the Philippines were attacked, the United States would not be bound to immediately react because the “constitutional process” mandates Congressional approval which, in turn, means a delay in American military intervention.
By contrast, Article 5 of the Washington Treaty forming NATO has something of a more immediate retaliatory clause. More recently, Lorenzana also inquired as to how the MDT would be applicable to cases of hostile actions short of “armed attack” such as China’s seizure of Mischief Reef in 1995 and Scarborough Shoal in 2012.
While citing the gains and prospects of upgrading the alliance, Lorenzana has likewise contended that the Cold War–era contextual relevance for the MDT is long past and that there no longer seems to be any threat of foreign attack. In addition, as tensions rise between China and the United States in the South China Sea, Secretary Lorenzana warned of strategic entanglement leading to “being involved in a war that we do not seek and do not want.”
The Reciprocal Defense Treaty
There are two scenarios for how the current conflict in the South China Sea could realistically trigger the MDT: an armed attack on the Philippines by a third party (presumably China), or on U.S. forces by the same. The first scenario is not outside the realm of possibility, given naval skirmishes between China and Vietnam in 1974 and 1988, and more recent calls from the Chinese defense establishment to take stronger actions that include the use of military force.
In the United States, the commander in chief can only introduce the U.S. military into hostilities if there is either a declaration of war by the U.S. congress, existence of a national emergency, or a statutory authorization by virtue of the War Powers Act of 1973, which was the case in Afghanistan in 2001 and Iraq in 1991 and 2002. Yet, there have been other cases where foreign military operations have been conducted without congressional approval: the 1999 air campaign in Kosovo, the 2011 bombing of Libya, and the 2017 surgical strikes on Syria. These precedents indicate that the U.S. could conduct immediate retaliatory strikes against China, should China attack the Philippines.
In the second scenario, the situation would be reversed, and the Philippines would have to go through its own constitutional processes. Like the U.S. Constitution, the Philippine Constitution accords the Philippine congress the power to declare “the existence of a state of war” and only upon such condition, or another national emergency, would the president be authorized by law to exercise the necessary powers “to carry out a declared national policy.” This means that the non-immediate retaliatory nature of the MDT not only applies to the United States, but also to the Philippines.
In spite of this congressional restriction, previous Philippine assistance to the U.S. has taken place without a declaration of war. For instance, in the years shortly after World War II, Clark Air Base in Pampanga was a “vital connecting link” for U.S. forces in South Korea. During the Vietnam War, Clark served as a strategic supply base and fighter-squadron installation. Throughout the Cold War, Philippine bases were a “major advantage” in U.S. containment strategy against the Soviet Union. Similarly, in the United States’ Global War on Terror, Philippine facilities were integral to U.S. combat operations in the Middle East by way of the Mutual Logistics Support Agreement. And with China’s more assertive posture in the South China Sea and the Rebalance to Asia strategy beginning in Barack Obama’s first term, previous Philippine president Benigno Aquino signed the EDCA.
An armed conflict between China and the United States is not impossible, even with economic interdependence and nuclear weapons raising the threshold for conflict. The current Sino-U.S. trade war, similar to tensions in the run-up to World War I, shows that political discord can override high-stakes economic relations. Similarly, limited wars between nuclear powers have been fought on two notable occasions, namely the 1969 Sino-Soviet Border Conflict and the 1999 Indo-Pakistan Kargil War.
China’s “gray zone tactics” in the South China Sea cannot be conventionally deterred by military force through the MDT, since activities like island building and interference in fishing or resupply missions fall outside the definition of “armed attack.” Thus, unless China draws first blood from either ally, the MDT will not provide a solution to the issue and the two countries must find other ways to address the conflict short of war.