For years, the Marine Corps has worked to shift its fighting focus back to the sea and how it might deploy larger units for its traditional amphibious ­assault mission if the United States faces a near-peer threat.

But right now, the Marine Corps does not even have enough ships to train for that contingency.

There are mounting worries among top Marine officials and defense experts who say that today’s Navy and Marine Corps are not sufficiently trained nor equipped to mount a large-scale invasion from the sea without catastrophic casualties and uncertain success.

The U.S. Navy’s fleet of amphibious assault ships would be vulnerable to coastal attack from a well-equipped enemy like China because the U.S. Navy ships lack the effective fires, sensors and combat formations to counter enemy ­defense systems, according to top military and government officials.

Moreover, today’s Navy fleet is too small to afford the Marines the opportunity to train for large-scale amphibious assaults.

While it’s common for the Corps to train with Marine Expeditionary Units, a force of about 2,000 Marines aboard multiple ships, the Navy is rarely able to provide enough ships for Marines to train in the larger formations that a real amphibious assault would require.

If the Marines were summoned for a large-scale maneuver from the sea, a well-equipped enemy would likely sink some of their ships and cause massive casualties, said one top Marine official.

“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 a recent talk to the Navy League.

Top Marine and Navy leaders have laid out plans for modernizing the Corps, ­especially how it integrates with the Navy while fighting in the ­contested “littoral zones” or areas a few hundred miles out to sea, into the ­beachhead and at shorter ranges inland.

They agree that the Corps’ Marine Expeditionary Units are well-trained, but near peer threats such as Russia, China, North Korea or Iran would require the use of a Marine Expeditionary Brigade or even a Marine Expeditionary Force.

The services’ forcible entry capability, a core competency of the Marine Corps and Navy team, is “at risk” above the MEU level, said Marine Lt. Gen. Brian D. Beaudreault, deputy commandant for plans, policies and operations.

“The ability to generate the number of ships required to train at a Marine Expeditionary Brigade level just simply isn’t there,” Beaudreault told the House Armed Services Subcommittee on Readiness during recent testimony.

The Navy and Marine Corps do not have enough amphibious ships to both fulfill their naval operations requirements and train at a level much higher than the MEU, he said.

Beyond the MEU, the Corps’ larger ­formations include a Marine Expeditionary Brigade with about 15,000 sailors and Marines. The Corps’ largest formation is the Marine Expeditionary Force, which can have more than 62,000 Marines and sailors at its disposal.

But Marines rarely assemble MEBs and MEFs for training or combat.

SHIP SHORTAGE

The concerns about the Navy’s ability to support the Corps’ amphibious assault capability raise fundamental issues about how Washington ­manages the military. Multibillion-dollar shipbuilding ­budgets are notoriously ­micromanaged by Congress and have long timelines that span both ­Republican and Democratic administrations.

Such long-term planning decisions for the current fleet were made in times of uncontested seas and when what are now near-peer adversaries lacked the capabilities to effectively deter and deny U.S. forced entry.

The size of the Navy fleet overall has been steadily shrinking for decades — and the amphib fleet is no exception.

In the 1990s, the Navy had 62 amphibious warfare ships; today it has 32.

Ideally, Marines would like as many as 50 amphibious warfare ships. Officially, current plans aim to reach 34 by fiscal year 2021 and an end goal of 38 by 2033.

The number of 38 was reached back in 2009 when the then commandant and CNO determined that they could fund 34 ships but would need 38 to support two MEBs, factoring in 10 percent of ships down for maintenance.

The ship shortage and its impact on Marine training was highlighted by a recent Government Accountability Office report.

The Navy could not fulfill 93 percent, or 293 out of 314, of the Marine Corps’ requests for amphibious training for the San Diego-based I MEF. And nearly half of the 40 requests from North ­Carolina-based II MEF went unfilled.

Cary Russell, the director of the GAO’s defense team, told lawmakers that the small fleet size and the current “ad hoc” way in which ships are assigned to ­Marine units awaiting deployment, fell “considerably short of being able to complete amphibious training operations.”

“If called on, these units could be left scrambling to obtain last minute training, risking their ability to be fully ready once deployed and underway,” Russell said.

But getting more ships may be a pipe dream when the Marines are competing in a tight budget environment with major Navy priorities such as next generation submarines, said retired Marine Col. David C. Fuquea, professor at the U.S. Naval War College.

“I get it, there’s not enough amphib ships, but there never has been and there won’t be in the future,” he said.

FIRES

Enemy shore defenses have improved significantly during the past 20 years. And while building more U.S. Navy ships would help, that alone will not solve the problem without better fires capabilities and sensors, he said.

Recently Marines have put the typically land-based High Mobility Artillery Rocket System, or HIMARS, aboard ships and struck targets on shore.

At the same time, they have asked industry for a mobile, shore-based ­anti-ship missile system to defend ­Marines ashore from attacks at sea.

Today’s Navy fleet is too small for the Marines to train for large-scale amphibious assaults. (Mass Communication Specialist Seaman Apprentice Jailene Casso/Navy)
Today’s Navy fleet is too small for the Marines to train for large-scale amphibious assaults. (Mass Communication Specialist Seaman Apprentice Jailene Casso/Navy)

But the stand-off ranges of up to 400 miles that some adversaries’ coastal defense systems provide may keep U.S. ships out of the fight if they can’t also be lethal, Coffman said.

“The amphibious fleet is a challenge with the price of entry in this age of fires,” Coffman said.

Though some experts have called for an increase in naval gunfire, adding 16-18-20 inch guns back onto ships, ­Coffman said the future is likely in ­rockets and missiles.

Marine Commandant Gen. Robert Neller has acknowledged some of those concerns about ships being ill-equipped for a large-scale fight.

“If the enemy has a capability to shoot my large ship or my destroyer or my ­carrier from a couple hundred nautical miles away — or maybe longer — I’ve got to do something about that,” Neller said in September at the annual Modern Day Marine conference in Quantico, Virginia.

“That’s why it’s important that all of these ships have the capability to do some sort of strike or denial, or some way to suppress that capability.

The solution may be tactical, Neller said. The Marine Corps does not plan to “land directly into the teeth of an enemy defense,” Neller said. Instead, the Corps will find gaps in an enemy’s defenses to put Marines ashore.

The Marine Corps also has options to disrupt or destroy enemy sensors and defenses, he said.

CRUISE SHIPS

Fuquea, the retired colonel, has long argued that the force must look at alternatives to amphibious assault ships for getting Marines to shore with the right equipment, and fast.

He said alternatives could include adopting tactical vehicles that will fit inside the V-22 Osprey.

Also, the retired colonel said that new civilian cruise ships can travel faster and carry more Marines than many amphibious ships. The Corps could use cruise ships, rigged with fast-moving boats on the side of the ships and refitted to hold gear and Marines for quick launches from farther distances.

Using commercially available boats such as the CB90, a fast attack assault craft that can carry a tactical vehicle and 18 Marines, units could move more fighters and the necessary equipment to the shore much faster, and cheaper, than in amphibious tracked vehicles, he said.

The boat travels nearly three times as fast as the current Amphibious Assault Vehicle in use to connect Marines from ship to shore.

Without enough gators, the Marine Corps has been experimenting with transporting Marines on other types of military and commercial ships.

During last year’s Koa Moana ­theater security exercise, Marines spent six months embarked on maritime ­prepositioning ships Pililaau and ­Sacagawea, both Military Sealift Command cargo ships, for training missions in Australia, New Guinea and Peru.

But alternative ships like these are not meant for combat operations, Lt. Gen. David Berger — now commander of MARFORPAC — said in March 2015.

“If you’re in a high-intensity conflict where you have to have a really tough time penetrating a high-end ­defense, you’re not going to plow in there with an aluminum hull anything, not for very long,” said Berger, who led I MEF at the time.

William Lloyd Stearman, a National Security Council staff member under four presidents, has argued for creating a “floating fortress” by converting a civilian supertanker used for shipping cargo into a heavily-armed platform that could launch helicopters, jets and boatloads of Marines and gear.

The concept would add firepower to enable the ship to both show force and produce enough offensive force to enter contested amphibious positions.

“The expeditionary ship’s very large deck could accommodate a variety of helicopters, as well as jet fighters and a fleet of drones,” Stearman wrote in a recent Wall Street Journal commentary.

“It could also store an array of offensive and defensive missiles in its hull, while defensive weapons would stand ready on the deck.”

He added that a supertanker ship’s complement would include a MEU-sized force or larger.

Peter Singer, a strategist for the New America Foundation and co-author of the book “Ghost Fleet: A Novel of the Next World War,” said to overcome the fires problem, Marines are looking at new methods to attack from the sea.

He said future amphib assaults will mean more landings deeper inland combined with shore assaults.

The Marines are already working with unmanned ships and other ways to take humans out of harm’s way in battle.

“Make it robotic…how do we use robotics to be in those first waves so that they’re the ones taking risks, forcing the enemy to reveal where their weapons are so that we can take them out?” Singer said.

Fuquea said that the distance ­provided by alternative connectors and ­platforms to deliver Marines to the fight could clear up funding to better arm the existing amphibious ships. He also argued that while the range of adversaries’ fires is longer, it isn’t necessarily as accurate.

Current methods require ships to be 12 miles offshore to deliver Marines to the beachhead, he said. But with different connectors, such as the CB90s and others, Marines could assault from over the horizon, as far as 100 miles from the beach.

That distance would increase the length of coast that the adversaries must protect, stretching their defensive capabilities.

Some of the mission remains similar to what the ­Navy-Marine-Special ­Operations Forces have done for decades, and expanding those joint ­operations will be key to future ­success, Coffman said. “Navy + Marine + SOF is the answer to the problem.”

But despite the concerns about ship shortages and adversaries’ ability to keep ships at a distance, Singer said, the Corps still has a unique capability.

“You could flip it the other way: For all of the complaints, it’s a capability that no other nation has,” he said.

Senior reporter Jeff Schogol contributed to this report.