American and Japanese troops attend the opening ceremony of the annual Yama Sakura exercise at Camp Kengun, Dec. 4, 2022. (Justin Nye/U.S. Army)

CAMP FOSTER, Okinawa — The Marine Corps will have a larger role in a joint U.S.-Japan virtual exercise scheduled for December that will focus on defending remote Indo-Pacific islands, according to Japanese officials.

The III Marine Expeditionary Force will send about 140 Marines to this year’s Yama Sakura, annual training to prepare for an attack or natural disaster, a spokesman for the Japan Ground Self-Defense Force said by phone Tuesday.

Held since 1982, Yama Sakura typically involves virtual and tabletop scenarios between the U.S. and Japanese armies, in what the military calls a command post exercise.

III MEF spokesman Capt. Pawel Puczko confirmed in an email Wednesday that Marines will take part in the exercise but would not say how many will participate.

This year’s training will take place primarily at Japanese bases Camp Asaka in Tokyo and Camp Kengun in Kumamoto, the Ground Self-Defense Force said in a news release Friday.

It will focus on the defense of remote islands in the Indo-Pacific “using cross-domain operations of the Japanese army, multidomain operations of the U.S. Army and the expeditionary advanced base operations of the Marine Corps,” according to the release.

Marines will participate “because of this feature of protecting remote islands,” the Ground Self-Defense Force spokesman said.

Members of III MEF previously had a relatively small presence in the exercise. Last year, about 10 members of the 3rd Marine Expeditionary Brigade participated, the spokesman said.

About 5,500 Japanese, 1,350 Americans and 250 Australians will participate in this year’s Yama Sakura, he added.

Some Japanese officials are required to speak to the media only on condition of anonymity.

Australia actively participated in the exercise for the first time last year after joining as an observer for a decade.

Troops from Japan, the U.S. and Australia planned the exercise at Camp Zama in early October, according to a U.S. Army news release Saturday.

The training will run concurrently with Warfighter, another tabletop exercise that will present “a dynamic, multi-day scenario to assess the readiness of units focused on the Indo-Pacific region,” the release said.

The Marines’ expeditionary advanced base operations call for mobile units to disperse inside the range of enemy missiles to seize and hold islands and sink enemy vessels at sea. It is one of the tenets of the Marines’ Force Design plan, which calls for the service to better defend the small islands east of Taiwan and to counter China.

“The lessons we learned in Resolute Dragon are now being built on in Keen Sword 25 and we will further develop them in Yama Sakura and other upcoming exercises,” III MEF commander Lt. Gen. Roger Turner said in a quote relayed by Puczko via email Oct. 29.