As the Rim of the Pacific exercise began wrapping up this week, Marines and soldiers from nine countries stormed Pyramid Rock on Monday morning at Marine Corps Base Hawaii.

It was the culmination of weeks of training by RIMPAC’s amphibious task force, commanded by South Korean navy Rear Adm. Sangmin An. It was also an opportunity for the U.S. Marine Corps to talk up its ambitious plans to reorganize its entire force, starting with troops on Oahu.

In March the service officially activated the 3rd Marine Littoral Regiment — the first such unit in the Corps — which is intended to bring the service back to roots as a force for island and coastal fighting but with an emphasis on high-tech weapons and communications systems.

Marine Corps Forces Pacific spokesman Maj. Nick Mannweiler said that the Corps is engaged in a “campaign of learning” as it works with other countries and refines its vision of a Marine Corps for the future.

“It’s entirely about ordering and supporting allies in their territorial integrity,” said Mannweiler. “So we think that there’s a lot of commonality in future training opportunities with them.”

The MLR made its debut overseas in April when it trained in the Philippines as part of Exercise Balikatan. The Philippines borders the South China Sea, which in recent years has brought it and other nearby countries into a series of territorial disputes with China, which claims almost the entire region as its exclusive territory.

The MLR appears tailor-made to operate in island nations in the Western Pacific as well as in disputed islands and reefs of the South China Sea, which also serves as a critical waterway through which more than one-third of all international trade travels.

Amphibious operations are among the most complex the military can carry out. On Monday, Australian army scouts landed ashore before the main landing force, keeping tabs on the beach and a nearby airfield from bushes on an overlooking hill. Then jets flew in to provide air cover just before helicopters swooped in on the airfield and landing craft pushed ashore, dropping off troops.

“(We’re) taking steps towards learning what naval integration is going to be like, how we actually do joint fires in this formation,” said Maj. Richard Larger, operations officer of the MLR’s 3rd Air Defense Battalion. “We’re going to take what we’ve learned here … and continue to pursue development and refinement through exercises slated to be conducted over the next few years.”

Among the lessons in the works is how to best handle logistics for MLR’s complex communications systems. Maj. Brent Logan, commander of the regiment’s communications company, said that effort is largely “an educational piece” through which joint and combined partners learn “what we do, because we’re so new.”

Logan said that the Marines worked closely with Korean and Australian forces in discussing how best to integrate their forces and complement capabilities. He added that training in the field at Marine Corps Training Area Bellows provided challenges that are already informing how the new unit will operate.

“We learned a lot about what equipment we need to get rid of and what equipment we need to bring with us, and what TTPs (techniques, tactics and procedures) we need to do to reduce our physical footprint and reduce our electromagnetic signature,” he said.

The MLR is intended to be light, agile and hard to find as it operates around the Pacific.

But much of the equipment it’s slated to use doesn’t exist yet. In the meantime the Marines are using stand-ins. During RIMPAC they used the HIMARS missile system as a stand-in for the NMESIS missile the corps eventually hopes to outfit its new units with to turn reefs and islands into anti-ship missile batteries.

The new vision of the Marine Corps has been controversial, particularly among some retired generals who say the new plan radically shifts the Corps away from its traditional role as a close-combat fighting force. But Maj. Mark Edgar, operations officer of the regiment’s 3rd Littoral Combat Team, said, “At its core, the littoral combat team remains an infantry battalion.”