The Marine Expeditionary Unit is floating force in readiness — hauling grunts, aircraft and tactical vehicles to rapidly respond around the globe.

But for the past 20 years the wars in Iraq and Afghanistan have been a major dumping ground for the roughly 2,000 Marines and their floating armada of combat power aboard the MEU.

It has sapped the Corps’ primary mission to fight from sea and secure ­contested beach heads.

As the Corps prepares to face down rival tech-adept forces like Russia and China, the Navy-Marine team will need to be more dynamic, unpredictable and able to spread across farther swaths of geography.

If you’ve blinked, you probably missed the signs.

But the Marine MEUs are once again at a major inflection point as they ­prepare for war with rising powers, a position the MEU has not been in since the Sept. 11, 2001, terror attacks.

At the forefront of those changes are the 13th and 31st MEUs — the current poster children for the commandant’s efforts to modernize a Corps stuck in the mindset of low-intensity war.

MEU developments could pose serious challenges and adaptations to the Corps’ culture as tenets align less with infantry and more with aviation, long range fires, intelligence — a break with historic norms.

Both MEUs have recently been part of historic deployments where they employed futuristic tech, new F-35 stealth aircraft and operated across a vast expanse of the globe, where Marines helped rekindle alliances and foreign partnerships across the Pacific Ocean.

The 31st MEU just completed a split operations exercise where forces were spread across the Indo-Pacific region in four different geographic regions.

The training evolution included the Whidbey Island-class dock landing ship Ashland operating in the South China Sea and the San Antonio-class amphibious transport dock Greenbay in the Gulf of Thailand, among other locations.

It was the largest simultaneous split operation by a MEU over such a ­geographic expanse, the 31st MEU says.

“We have had our forces arrayed over a 4,000-mile area of operations,” Col. Robert Brodie, the commander of the 31st MEU, told Marine Corps Times.

The 13th MEU’s deployment comprised of operations in four different fleet area of operations and three different combatant commands, from the ­Mediterranean Sea to the Indo-Pacific.

“We had Marines in 25 different countries during this deployment,” Col. Chandler Nelms, commanding officer, 13th Marine Expeditionary Unit, told Marine Corps Times. There were 16 theater security cooperation exercises with foreign partner forces and unilateral training events.

“And we were supporting real-world operations while we were conducting those exercises with daily flights of F-35s.”

Those F-35 operations included the first ever combat strikes by high-tech stealth fighter in Afghanistan in September.

The F-35 also carried out strikes in support of anti-ISIS operations known as Operation Inherent Resolve, or OIR, in Iraq and Syria.

Between Afghanistan and OIR, the F-35s with the 13th MEU racked up over 50 flying days, 1200 direct combat support hours and dropped ordnance in both theaters, according to Lt. Col. Kyle Shoop, commanding officer, Marine Fighter Attack Squadron 211.

But the 13th MEU’s support of combat operations in U.S. Central ­Command was not the central focus of the MEU, where only a small part of the force

even went ashore for anti-ISIS operations.

“We also spent a lot of time in other areas, specifically 7th Fleet. Sometimes you know you think of 7th Fleet as something we just pass through,” said Capt. Gerald Olin, commander, ­Amphibious Squadron One.

The 7th Fleet are of operations ­comprises much of the Indo-Pacific region — a region of great significance to the new defense strategy aimed at confronting great power challenges, like China’s rapidly rising naval and military capabilities.

The MEU and its Navy team carried out partner building exercises in ­Malaysia, Indonesia, Sri Lanka and ­India — important allies that could prove pivotal in any fight with China.

One such development was the first-ever landing of an Indian ­helicopter on the deck of the U.S. amphibious transport dock ­Anchorage, as part of an agreement known as ­Helicopter Operations from Ships other Than Aircraft Carriers. Olin characterized the Anchorage’s engagement with India as “fairly large,” which also included Indian landing craft operating in the ship’s well deck.

The MEU spent nearly three months, almost half the time of a traditional MEU deployment cycle, in 7th Fleet — a quasi-pivot of the Corps’ U.S. West Coast MEUs to the Pacific after years of beelining and focusing on the Middle East.

The 31st MEU is always ­forward-deployed and headquartered out of Okinawa, Japan. It is the premier crisis response force for the ­Indo-Pacific region.

The last big MEU change

It’s a far cry from the days when a significant portion of the Marine ­air-ground task force would wade ashore in support of major combat operations in the Middle East.

As was the case for the 13th MEU embarked aboard the amphibious assault ship Tarawa in the fall of 2005, when its Marines waded into Iraq to support Operation Steel Curtain.

That time was also a time of change for the Corps, as the Marines were trying to hone skills for counterinsurgency and were learning how to defeat roadside bombs that lined Iraqi streets.

The grunts on that MEU with 2nd Battalion, 1st Marines, would help clear towns and villages such as Husaybah, Karabilah and Ubaydi, which were chock full of militants and al-Qaida terrorists streaming across the Syrian border.

The Marines called the operation “Fallujah lite”— an ode to the bloody battle by 2/1 to clear Fallujah in 2004, retired chief warrant officer 2 Michael D. Fay told Marine Corps Times. Fay was a combat artist embedded Fox company 2/1 during its assault on Ubaydi, Iraq.

The Marines of 2/1 he said, were “salty sons of bitches,” with combat experience from the prior operation to clear Fallujah.

But the Corps was still learning how to kit up its grunts with the ­necessary optics and tech to take on Iraqi insurgents. Some Marines were carrying M16A4s and others had M4s, and not everyone had a rifle optic like the ACOG either, Fay said.

The two big deck amphibious assault ships from the 13th MEU’s 2018 deployment and 2005 would easily be discernible from each other.

The Marines who took on Iraqi insurgents and al-Qaida militants in towns and villages along the Euphrates River were hauling CH-46s and AV-8 ­Harriers, not MV-22s and F35s like today.

But it’s not just the employment of the F-35 that makes today’s 13th MEU historic, nor is it its reduced focus on CENTCOM.

It’s the nature of the ­deployments, which included extensive ­experimentation for future war and saw itself spread across vast geographic terrain and was more dynamic in the employment of its assets.

The “ship moved around a lot,” Olin said.

It’s an example of then-Secretary of Defense Jim Mattis’ dynamic force concept, which challenges the military to be less predictable and more nimble.

“It’s not so much the case as going to one place and staying there the whole deployment,” Olin said. “It’s the ability to operate in any theater at any time.”

The ships that comprised amphibious ready group for the 13th MEU ­included the amphibious assault ship Essex, amphibious transport dock ­Anchorage and amphibious dock ­landing ship Rushmore.

“We move our ships around when we want them to be in certain places, so we have them where we want them,” Olin explained.

The 13th MEU was also at the forefront of experimenting with various fighting concepts key to the Corps’ plans to confront Russia and China.

The 13th MEU participated in the 2017 Dawn Blitz exercise, where rocket artillery known as HIMARS were fired from the deck of the Anchorage at ­land-based targets.

The HIMARS ship-to-shore test proved an important capability for the Corps to help extend range and lethality of its forces but also bolster the security of the Navy’s amphibious ships against high tech rivals armed with ship killing long range cruise missiles.

Nelms also said the 13th MEU carried forward more experimentation of the Corps expeditionary advanced base operations concept, which will see ­Marines spread thinly across floating barge bases, islands and ships across the Pacific.

The distributed force will aid the Corps in surviving in a fight in the Pacific, while denying China the ability to focus its fire power in one area.

Tech and adversaries are pushing transformation

The MEU is currently at a major inflection point after nearly 20 years of supporting operations in the Middle East.

And tech, like the F-35, and rising adversarial capabilities are helping fuel that change and drive the MEU to be more agile.

“What’s driving this and enabling this is purely the dynamics of the theater,” Brodie said about the 31st MEUs distributed operations.

Moreover, the F-35 is bringing extra capabilities that are affording the MEUs the ability to address all of its essential mission tasks from ­humanitarian disasters to addressing adversaries with advanced military capabilities.

The 31st MEU was the first to load bombs externally and internally on the F-35. The reason for doing this, Brodie said, was to ensure “the F-35s are capable of doing their entire mission set.”

The challenge is arraying forces and the F-35s in a way that “creates ­dilemmas for an adversary” and “creates “friction and fog of war for them,” while also maintain command and control of the force.

The stealth F-35 fighter “brought a lot of capability to defend the ­amphibious task force that we didn’t have with the AV-8 Harrier,” Olin said.

The 13th MEU was able to use and experiment with the F-35 in roles that it was not able to with the legacy Harriers, such as a deck launched ­interceptor and a defensive counter-air and anti-surface combat role.

This allowed the MEU to use the aircraft more like what would be seen with carrier-based aircraft, according to Olin.

Data fusion and the networked capabilities of the F-35 also boosts the amphibious task force’s overall security.

The sensors on the F-35 provide the “ability to see at a real high fidelity a lot of detail in a very wide operational space, and then to share that picture, that understanding, with not only aircraft, but with ships and units ashore,” Dakota Wood, a retired Marine officer and senior fellow with the Heritage Foundation, told Marine Corps Times.

Those sensors can help redirect fires from other assets. The Marine Corps ­already has successfully tested a ­successful HIMARS shot using a data link between the F-35 and the ­ground-based rocket artillery.

These developments will prove handy, as in a future war the Corps will be up against adversaries that have been pushing the ranges of artillery and cruise missile systems.

What’s old is new again

The dynamic nature of the recent MEU deployments isn’t necessarily a new concept, Wood explained. It’s just new for the current Marine Corps.

When Wood was on the 26th MEU in the mid-90s it had a ship in the Adriatic Sea to respond to a potential non-combatant evacuation operation or potential embassy reinforcement in Albania, a ship doing a bilateral exercise with the Spanish and the big deck ship off the coast of West Africa for a potential operation in Zaire.

A lot of the concepts about distributing the force and Navy ships over vast geographic terrain were well-practiced during the Cold War, they just took a back seat after 9/11 as the military’s ­attention focused on ­counterinsurgency and the Middle East.

“The military has to relearn things that it new very well in the past,” Wood said. The Corps is now “having to figure out what that really means in terms of logistical support and extended command and control. You have a MEU commander and he’s got Marines in 20 different countries, how do you manage that?”

But he also warned that for the Corps to continue to be more ­dynamic and operate its MEUs at greater distances apart will require more ­amphibious ships.

The Corps has argued it needs as many as 50 amphibious ships. That ­amphib fleet size would also better ­enable the Corps to conduct more training for its amphibious mission.

But with Russian and Chinese forces continuing to develop sophisticated tech aimed at sinking U.S. naval ships, more amphibs will serve as a backdrop in case some ships are destroyed.

“Guess what? Some of our ships are going to go to the bottom with these great sailors and Marines,” Marine Maj. Gen. David Coffman, director of expeditionary warfare for the chief of naval operations, said at the Navy League in early 2018.

There is a current goal of 38 amphibs by 2033. But Breaking Defense reported that the Pentagon plans to cut two amphibious ships from the 2020-2024 budget, putting the Corps’ mission to capture contested beach landings at considerable risk.

Less infantry focus?

The 13th and 31st MEUs recent deployments were a premier example of the Corps recent drive to modernize its force and prepare it for future war.

The MEUs were more dynamic, and able to operate at vast distances, employ future tech, experiment with HIMARS, operate high-tech stealth aircraft and carry out distributed operations.

But a recent Rand Corp. study warned that the Corps’ drive for new tech and distributed operations could drive a wedge in its infantry-centric model.

“Emergent Marine Corps concepts and capabilities may be shifting the center of gravity for Marine combat power away from infantry toward ­aviation and artillery for certain scenarios, marking a significant break from the historical practice,” the study reads.

Those scenarios within the expeditionary advanced based operations concept would see infantry act more as an enabler in a Pacific fight to aviation and rocket artillery operations.

“The shifting locus of combat power and operating concepts may trigger a subtle shift in emphasis within ­Marine Corps culture from supporting infantry to supporting the MAGTF,” the study reads.

But Wood said he believed Rand may be overstating the case.

“Not everything is going to be this long-range fires fight,” he said. Marines deployed 800 miles away on Ospreys are still going to need sufficient lethality of their own to survive a fight.

Skills like patrolling urban environments and gathering intel from local populations are not going to go away. The Corps is always going to have a ­requirement for “getting down and dirty in the weeds,” he said.

Pushing the focus away from the infantry would also impact the kinds of missions the Corps is frequently called upon to do, Wood added.

And the Corps appears to still be sinking a lot of investment in its grunts.

The commandant has pushed new tech, automatic weapons, night vision, tablets and drones, all to boost lethality of the infantry.

And coming up next, the 26th MEU, with 2nd Battalion, 8th Marines, will experiment with a 15-man rifle squad for an upcoming deployment.

Grunts have argued that the 15-man squad is necessary for infantry Marines to hone and manage all the new tech like drones and tablets dropped in their laps over the past couple of years.

The 15-man squad will also boost the survivability of the Marine infantry in a Pacific fight.

Ground combat reporter Todd South contributed to this report.

Shawn Snow is the senior reporter for Marine Corps Times and a Marine Corps veteran.