ITBAYAT, Philippines (AP) — U.S. Marines and their Filipino counterparts darted out of Black Hawk helicopters during combat drills Monday in the Philippines’ northernmost island town along the strategic Bashi Channel off southern Taiwan — a flashpoint in the military rivalry between Washington and Beijing.

The show of allied battle readiness in Itbayat in Batanes province is part of annual military exercises that started last month, dubbed Balikatan, Tagalog for “shoulder-to-shoulder,” and involving more than 16,000 American and Philippine military personnel.

This year’s exercises by the longtime treaty allies — the largest yet — are meant to deter possible aggression. They come against the backdrop of China’s increasingly assertive actions in the disputed South China Sea, where Chinese and Philippine coast guards and accompanying ships have had several increasingly tense faceoffs since last year.