The Marine Corps just wrapped up a pair of ambitious multiservice island-­hopping exercises, offering a blueprint for how it plans to fight in the Western Pacific by bringing to bear fast-moving and highly connected forces from the Army, Navy, Air Force, Marines and Space Force.

Exercises Castaway 21.1 in Japan and Spartan Fury 21.1 in Hawaii were linked and conducted on five islands including Okinawa and nearby Ie Shima as well as Oahu, Kauai and Hawaii island.

About 1,000 personnel were involved in the March 1-20 training.

“We know that everything in the future is going to be joint (service operations),” said Col. Michael Roach, Okinawa-based commanding officer of the 12th Marine Regiment and overall mission commander for the exercises. “The way the Pacific is, you have to be. You have to fight joint and coordinate joint to be successful.”

China already has the world’s largest land force and navy and sophisticated missiles to keep U.S. forces at bay. The Marines and Army want to deter China by developing ground units that can seize islands and sink ships with missiles.

The U.S. military as a whole hopes to gain an outsize advantage by greatly meshing Army, Navy, Air Force, Marine and Space Force capabilities on land, sea, air, space and cyberspace.

Ultimately, the goal of the Okinawa and Hawaii exercises was projecting power quickly with missile units dispersed across islands in support of Navy ships.

Operations on Ie Shima included:

>> Reconnaissance Marines, Army Special Forces and Air Force special operators arrived by parachute via MV-22B tilt-rotor Osprey and amphibious infiltration under cover of darkness to scout for enemy forces and determine the airfield’s suitability.

>> Support came from several F-35B short-takeoff and vertical-landing fighter aircraft.

>> Hundreds of Marine infantry arrived by Ospreys and helicopters.

>> A High Mobility Artillery Rocket System truck was flown in using a Marine Corps KC-130 aircraft with the 3rd Battalion, 12th Marines simulating firing missiles at ships at sea.

>>Infantry from the 3rd Battalion, 3rd Marines set up coastal defenses on a portion of Okinawa and used low-profile boats to strike targets at sea.

During Exercise Spartan Fury in Hawaii, meanwhile:

>> Army Logistics Support Vessels, big cargo carriers that can pull up on a beach, transported 1st Battalion, 12th Marine personnel, artillery and trucks from Oahu to both the Pacific Missile Range Facility on Kauai and the Big Island.

>> An Air Force C-17 cargo aircraft flew an Army HIMARS rocket launcher truck and specialized Army “Multi- Domain Task Force” from Fort Lewis, Wash., to the Pacific Missile Range Facility to simulate missile launches.

>> Marines worked directly with the Pearl Harbor destroyer USS Halsey, using its sophisticated sensors to provide improved targeting information.

The exercises also utilized small unmanned aircraft and satellites to share targeting information. Resupply to the islands was conducted by Osprey, helicopters and C-130 aircraft.

Carl Schuster, a retired Navy captain and former director of operations at U.S. Pacific Command’s Joint Intelligence Center, said the exercise “does represent a significant step forward in joint training in the Indo-­Pacific theater.”

It also demonstrates that command, control, communications, computer systems, intelligence and surveillance have become better integrated.

“No nation on this earth can match that capability,” Schuster said. “More importantly, it greatly complicates any enemy’s efforts to maintain control over any uninhabited or recently occupied islands in ocean areas it may desire to control.”

Potential adversaries “have no choice but to take note” of the capability, he added. “This shows the inherent flexibility and reach of U.S. joint forces, including their ability to hit at long range and move. That complicates an enemy’s planning and targeting.”

Roach, the mission commander, said that with so many disparate forces, the exercises were not the easiest to organize.

“For me personally, as an artillery regimental headquarters, this is the first time that we’ve had a scale of jointness” like this with other services and skill sets, he said.

But getting those forces to participate “was an easy sell.” Roach said that “everyone bought in. (We) got tremendous buy-in from all the senior leaders who are seeing that there’s a need to be joint, there’s a need to be maritime. So it’s an open door that we’re being welcomed in to put these opportunities together.”

That doesn’t mean that everything went exactly according to plan. The ability to communicate across serv­ices and platforms is one sticking point.

“I would say we found challenges, we found opportunities,” Roach said in an interview. “I mean, I would be lying to say it worked perfectly.”

But, he said, “we found ways to work around that. We’ve certainly found unique ways to make sure we create that digital link to close that decision cycle, but there’s a way to go.”

The artillery regimental commander said he “absolutely” expects Marines to operate a lot more with Army Logistics Support Vessels that are based in Hawaii. The Navy is pursuing a new class of vessel called the Light Amphibious Warship for Marines, but in the interim the Army beach-­landing vessels provide “such a unique capability that can’t be replicated right now.”

He also said the 1st Battalion, 12th Marines in Hawaii will evolve from its traditional cannon artillery role as the service shifts toward greater emphasis on island operations and missile forces.

The artillery battalion “is going to have a capability in the future to be more lethal or be more capable for a maritime operation,” he said.

Roach said in future iterations of the exercises, he’d like to see allies participate.

Going through the exercises, one thing he learned was that “what makes the ‘hard’ easier is attitude,” he said. “The attitude we found with the joint forces that are on sometimes different tactical data links, sometimes using different radio systems, is complicated, but the attitude we have with everyone wanting to find solutions just created a solutions-based environment.”

That high level of cooperation across services will be necessary in future warfare.

“You need a joint approach, but you also need to be fast (moving). I would say fast and thinking,” Roach said. “So when you have joint partners that are integrated on a common network that can out-cycle an adversary’s decision, then you’ll be successful.”