By Chelsea Robin | 2026-07-09

The United States and its allies are strengthening military cooperation around the "first island chain" through a series of joint exercises designed to improve interoperability and reinforce regional deterrence, analysts say.

Recent exercises centered on the strategic island chain stretching from Japan through Taiwan and the Philippines before curving toward the southern reaches of the South China Sea. They overlapped with the Rim of the Pacific (RIMPAC) 2026 exercise in and around Hawaii, creating a broad arc of allied training across the western Pacific.

Operation Pathways comprises 53 exercises conducted across the Indo-Pacific during May and June and again in September and October, U.S. Army Gen. Ron Clark said June 23.

"The reason for that is that's when the sea states are favorable for a cross-strait invasion from mainland China to Taiwan," Clark said, according to the Association of the United States Army.

"So, if our highest duty is to deter war ... we have to have combat credible forces forward through an exercise program that allows us to position ourselves in advantage at the invitation of partners and allies to deter war," he added.

Japanese and U.S. forces recently hosted two major exercises aimed at improving interoperability and island defense. Exercise Valiant Shield 2026 ran June 22–July 1 and involved forces from Australia, Canada, Japan, New Zealand and the United States.

Exercise Resolute Dragon 2026 took place June 20–30, bringing together Japan's Ground Self-Defense Force (JGSDF) and the U.S. Marine Corps' III Marine Expeditionary Force.

"For the United States Pacific Command, the U.S. commitment to allies' security along the first island chain is sacrosanct," Hunter Marston, director of the Southeast Asia Program and lead of the Asia Power Index at Sydney's Lowy Institute, told the South China Morning Post.

Valiant Shield expands

Led by U.S. Indo-Pacific Command, Valiant Shield took place in the Northern Mariana Islands, Guam, Japan and surrounding waters.

Originally a U.S.-only exercise, the biennial event has evolved into a multinational joint field training exercise. This year marked the second time the Japan Self-Defense Forces were fully integrated into planning and execution, according to USNI News.

"Valiant Shield demonstrates our enduring commitment to a free and open Indo-Pacific," Adm. Steve Koehler, commander of the U.S. Pacific Fleet, said.

"Exercising advanced multidomain capabilities with our allies ensures we continue to seamlessly innovate and operate together, project combat power together and prevail over any challenge -- together."

About 10,000 personnel trained in antisubmarine warfare, drone operations and multinational maritime strike missions. The exercise culminated in a sinking exercise (SINKEX) of the decommissioned amphibious transport dock USS Juneau (LPD-10) in the Philippine Sea.

Air, surface and subsurface forces coordinated strikes in practicing weapon employment and target engagement under realistic combat conditions, the U.S. Navy said.

"This SINKEX provided an outstanding opportunity for our joint team to integrate capabilities across domains, honing the lethal precision and coordination essential for high-end maritime operations in the Pacific theater," Rear Adm. Eric Anduze, commander of Carrier Strike Group 5 and Task Force 70, said.

The final strike that sank the USS Juneau came from a Japan Maritime Self-Defense Force (JMSDF) submarine. The Japanese military posted images of a JMSDF SH-60 helicopter firing an AGM-114 Hellfire missile and a JMSDF destroyer launching a Type 90 antiship missile.

Island defense

About 9,000 personnel from the III Marine Expeditionary Force and the JGSDF's Western Army trained in the concurrent Resolute Dragon exercises.

Held annually since 2021, Resolute Dragon focuses on strengthening command-and-control, multidomain maneuver and island defense capabilities.

The JGSDF said the drills were intended to "improve bilateral interoperability for island defense operations and further strengthen our bilateral deterrence and response capabilities."

Training took place across Kyushu, Okinawa and the southwestern Nansei island chain, including Miyako, Ishigaki and Yonaguni.

China's response

China has expressed concern over growing U.S.-Japan military activity around Taiwan and the first island chain despite the exercises' stated defensive focus.

Of particular concern to the People's Liberation Army Navy is the participation of the U.S. 12th Marine Littoral Regiment from the 3rd Marine Division, according to the Maritime Executive.

The regiment, permanently based at Camp Hansen in Okinawa, received two new coastal defense systems in June: the Navy-Marine Expeditionary Ship Interdiction System (NMESIS) and Marine Air Defense Integrated System (MADIS).

"The NMESIS and MADIS represent a significant step forward in the Marine Corps' modernization efforts," the 3rd Marine Division said, adding that the systems provide land-based antiship and counter-small unmanned aircraft capabilities.

Strategic shift

The recent pattern of military exercises reflects Washington's evolving Indo-Pacific strategy, analysts say.

For years, the United States emphasized broad security partnerships across South and Southeast Asia. Increasingly, however, it has concentrated military planning on the first island chain, said Sarang Shidore, director of the Global South Program at the Quincy Institute for Responsible Statecraft.

"Washington has shifted its security strategy toward China," he wrote July 7, adding that the United States is now focused on "a narrower, militarized line of defense, specifically the first island chain, which runs from Japan to the Philippines."

Since releasing its National Security Strategy last November, Washington has placed greater emphasis on partnerships within the "Squad," comprising Australia, Japan, the Philippines and the United States.

"All four Squad members are treaty allies, all are unambiguous about its role as a defense group and all are better positioned around the geography that actually matters militarily," Shidore wrote.