By Adrien Chorn and Monica Michiko Sato – October 1, 2019, CSIS
On August 31, 1951, representatives of the United States and the Republic of the Philippines signed the Mutual Defense Treaty (MDT) in Washington. In recognition that “an armed attack in the Pacific Area on either of the Parties would be dangerous to [the] peace and safety” of both countries, the treaty declared that each state would “act to meet the common dangers in accordance with its constitutional processes.”i However, like most conventional defense treaties and standards, the MDT is not clear about the increasingly common unconventional gray zone threats that skirt the definition of war to avoid prompting a kinetic response. Since its inception, the United States’ commitment to the MDT regarding attacks on Philippine assets in contested waters in the South China Sea has been unclear.
