Members of the 15th Marine Expeditionary Unit walk down a pier during the Archipelagic Costal Defense exercise at San Vicente in Palawan, Philippines, May 18, 2024. (Donald Holbert/U.S. Marine Corps)

Members of a Marine Corps rotational force are on their fourth exercise in the Philippines since March, creating a near-constant presence by U.S. forces in the country as tensions simmer between China and the American ally.

A company from Marine Rotational Force-Darwin began 23 days of training Monday on the western island of Palawan alongside the Philippines’ 3rd Marine Brigade, according to a force news release Tuesday. A company is typically composed of between 150 and 200 Marines.

The Archipelagic Coastal Defense training was designed to enhance readiness in environments found throughout Southeast Asia. It includes marksmanship, patrolling, jungle survival and drone training and culminate in an airfield seizure exercise at Roxas Airfield, Palawan, according to the release.

“It’s showing our operational reach from Australia,” Col. Jason Armas, commander of the 2,500-strong rotational force, told Stars and Stripes by phone Thursday. “We are extending forward into the first island chain.”

The Australia-based force’s extended presence in the Philippines comes amid increased tension between Manila and Beijing in the South China Sea. China’s coast guard employed a water cannon to expel a Philippine Bureau of Fisheries vessel at Scarborough Shoal on Friday, according to media reports.

A major clash on the sea, most of which Beijing claims as its territory, could involve U.S. forces. Washington has vowed to defend Manila, a treaty ally, if it is attacked.

The rotational Marines began their Philippine training in spring as the bulk of the force arrived in Australia’s Northern Territory to kick off its annual six-month deployment.

Members of Marine Rotational Force-Darwin visit the western coast of Palawan, Philippines, during a Balikatan drill on April 28, 2025. (Seth Robson/Stars and Stripes)

A company of rotational Marines traveled to the Philippines’ southern island of Mindanao in mid-March and joined Marine Exercise 2025.

In April, force Marines were in Palawan for the Balikatan exercise. And in May, members of the force participated in the annual Kamandag drills.

Some rotational Marines may be in the Philippines later this year, when others head to Indonesia for the Super Garuda Shield exercise, Armas said.

Marine Rotational Force-Southeast Asia, which typically arrives in the fall, has also trained regularly in the Philippines since it was formed in 2022.

The Marines’ lengthy training stints in the islands don’t equate to a permanent presence, retired Marine Col. Grant Newsham, a senior researcher with the Japan Forum for Strategic Studies, told Stars and Stripes by email Friday.

“But as a practical matter, if the rotation schedules are done right it’s possible to have Marines around in the Philippines almost constantly,” he wrote. “And if they are doing useful things — i.e. specific training, exercising, and constant interaction and joint activities with the Philippine forces — this is a very good thing.”

Rotational forces in the Philippines avoid financial, logistical, infrastructure, personnel and political headaches that come with having a traditional permanent presence, Newsham said.

Members of the Darwin-based force have also practiced disaster response in New Caledonia with French forces and explosive ordnance disposal in Papua New Guinea, Armas said.

The force is preparing for the biennial Talisman Sabre exercise, which is scheduled to involve 19 nations training across Australia and Papua New Guinea from July 13 to Aug. 4.

A Marine Air-Ground Task Force will operate alongside Australian army brigades, treating parts of the Northern Territory as if they were small islands, Armas said.

The rotational Marines will hone expeditionary advanced basing skills, he said, referring to a strategy of using small, mobile, forward bases for rapid, widespread operations.

During Talisman Sabre, “we are going to use the totality of the Top End to really expand our operations here,” he said.