Why would the US defend the Philippines?

MANILA, Philippines — Relations between the United States and the Philippines have been in overdrive since President Ferdinand Marcos took power in June 2022, fuelled by China's growing assertiveness in the Asia-Pacific region.

A key concern has been the South China Sea, where repeated confrontations between Chinese and Philippine vessels near disputed reefs have raised fears of a wider conflict involving the United States and other allies.

The issue was high on the agenda of Thursday's first trilateral summit between the United States and treaty allies Japan and the Philippines.

AFP looks at the deepening of defense ties between the Philippines and the United States, and why Washington could go to war for Manila.

The Philippines is a major focus of US efforts to strengthen regional alliances due to its close proximity to the South China Sea and self-ruled Taiwan, which China claims as part of its territory.

While Manila and Washington have a complex history that has seen relations see-saw in recent years, they have remained bound by a 1951 Mutual Defence Treaty.

Top Biden administration officials have repeatedly said that "an armed attack" against Philippine public vessels, aircraft, armed forces and coastguard anywhere in the South China Sea would invoke the treaty.

In 2014, a defence cooperation agreement between the two countries gave US troops access to five Philippine military bases.

That pact became dormant under former president Rodrigo Duterte, who was pro-China, but was revived and expanded after Marcos came to power and now includes four additional sites.

"Given the geopolitical situation now... the messaging of the US commitment to the Philippines is more clarified and more coherent," said Andrea Wong, a non-resident research fellow at the Institute for Indo-Pacific Affairs in New Zealand.

The South China Sea covers more than three million square kilometres and is the main maritime link between the Pacific and Indian oceans, giving it enormous trade and military value.

Its shipping lanes connect East Asia with Europe and the Middle East, with trillions of dollars in ship-borne trade passing through the sea annually.

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