Members of the Southeast Asia Maritime Rotation Force stand in formation with Indonesian marines to launch Naval Exercise Keris on Nov. 6, 2024, in Batam, Indonesia. (Shaina Jupiter/US Marine Corps)

A Marine Corps rotational force is getting to know a part of Indonesia it hasn’t seen before, an area close to a potential flashpoint with China.

About 200 members of the Marine Rotational Force-Southeast Asia are at Indonesian naval base Yonif 10 Marinir on Batam Island east of Singapore, the force’s commander said on Thursday.

The island sits next to the 19-mile-wide Singapore Strait, a strategically important waterway through which thousands of merchant ships travel to and from the South China Sea every day. Beijing claims almost the entire sea as its territory.

Indonesia’s Natuna Islands, located in the South China Sea northeast of Singapore, are close to waters near China. Indonesian fishermen have reported intimidation by Chinese coast guard ships near the islands in recent years.

The Chinese also harassed Vietnamese fishermen and interfered with Philippine attempts to resupply an offshore maritime outpost elsewhere in the South China Sea.

Returning force Marines left Manila for Singapore after participating in exercise Kamandagh with Philippine forces last month, their commander, Col. Stuart Glenn, told Stars and Stripes by phone from Batam.

He said they were reinforced by members of the 2nd Battalion, 7th Marine Regiment, from Twentynine Palms, California.

The Marines took a commercial fast ferry from Singapore to Batam, home to Indonesia’s 10th Marine Battalion. According to Glenn, this is the first time U.S. Marines have trained in this part of Indonesia, where monkeys and cobras are also found.

“We feel like we are working in the tropics,” he said.

They are taking part in the third annual Keris Naval Exercise along with 360 Indonesian sailors, starting on Wednesday and continuing until November 19. During last year’s training, 150 members of the rotational force conducted a coastal defense exercise in West Java, Indonesia.

Glenn said the country’s mariners were “trying to move toward a coastal defense capability” with their local counterparts this month.

He added that the training includes fire support control, planning, maneuvering, jungle survival and medical training.

“Keris MAREX will culminate in a final training event that will pit a joint force of Indonesian and U.S. Marines against a significant adversary attempting to conduct an amphibious landing,” the rotating force said in a statement Wednesday.

Force-based and live-fire training involving small arms and mortars is planned for Singkep Island, a four-hour ferry ride south of Batam, Glenn said.

“It’s a three-canopy forest and it’s a remote place,” he said of the island without an airport. “This will stress small unit leaders on both sides.”