How the Marines and the Navy work together on the high seas

The seven-month odyssey of a "blue-green" flotilla that saw combat in Yemen and Syria and conducted training exercises across a large swath of the globe demonstrates the enduring importance of the Navy-Marine Corps team overseas, commanders of the 11th Marine Expeditionary Unit said May 24.

Departing San Diego on Oct. 14, the 11th MEU and the Makin Island Amphibious Ready Group reportedly supported a Jan. 29 raid in Yemen in which a Navy SEAL — Chief Petty Officer William "Ryan" Owens — was killed. They also brought artillery and infantry troops to Kuwait for later duty, providing firepower to Kurdish partners besieging Raqqa, the Syrian city that doubles as the capital for the terrorist Islamic State.

The howitzers manned by the Marines conducted more than 400 fire-support missions in Syria, firing more than 4,500 shells at ISIS targets, according to the 11th MEU.

"It was the right Marine air-ground task force to provide supportability, mobility, and lethality," 11th MEU spokesman Maj. Craig Thomas said during a news conference May 24 at Camp Pendleton. "The Marines supported local Syrians who are fighting to rid ISIS from their country."

Also read: Marines arrive in Syria to support assault on ISIS capital

Citing the classified nature of the Yemen operations, Thomas said he couldn't comment on that raid.

His report card for the MEU comes during a series of debates not only about America's policies toward Yemen and Syria but also grumbling concerns about the future of Marine expeditionary units.

Experts continue to fret about how Marine battalions will conduct their amphibious missions in an age of super-fast and precise, long-range anti-ship-air missiles, plus Pentagon budget woes that appear to prioritize submarines and destroyers over amphibious assault ships like the Makin Island.

That flagship vessel returned to San Diego on May 15. It and the fellow amphibious assault ships Somerset and Comstock combined to carry more than 4,500 sailors and Marines, spending three months in the Pacific Ocean and four months in the waters off the Middle East and Africa.

Beyond the combat operations in Syria, the group held exercises in Hawaii, Guam, Papua New Guinea, Malaysia, Djibouti, Oman, and the Persian Gulf. Marines also stood ready to evacuate the embassy in the South Sudanese capital of Juba during hostilities there — the sort of mission that makes an amphibious ready group and Marine expeditionary unit "the 9-1-1 organization from the sea," 11th MEU commander Col. Clay Tipton said.

Retired Marine Col. Mark Cancian — a senior adviser with the Center for Strategic and International Studies, a nonpartisan think tank based in Washington, D.C. — echoed Tipton's perspective that the MEU remains a lasting example of flexible armed response from the sea.

"What makes a Special Purpose Marine Air-Ground Task Force so valuable is the ability of the Marines to mix and match capabilities," Cancian said. "That's what they're doing and that's what they should be doing."

And that's particularly important for Syria because how the Marines were used dovetails with President Donald Trump's foreign policy goals — defeat the Islamic State without putting too many boots on the ground, he added.

"The thing that the Marine Corps can provide that's really needed is fire power for allies like the Kurds or Iraqis — artillery, mortars, aircraft," Cancian said. "So far, Trump's policy has been adamant about not using infantry, except in a limited role to protect artillery and other units that are on the ground to add firepower for allies."

If the mission in Syria grows, Cancian could envision Marine and Navy logistical heft toting more supplies to Kurdish militias or the Free Syrian Army, perhaps even occupying an airfield and using it as a forward operating base. The Corps also could deploy more artillery observers and so called "Joint Terminal Attack Controllers" who call in airstrikes, but Cancian doubts the White House would land a large number of "boots on the ground."

"The tough question on Syria is the same as the one in Iraq: What happens next, after ISIS is defeated? ... That's a huge fork in the road for the Trump administration, but it's still months away," he predicted.

Potential rivals at sea such as Russia, China, and Iran increasingly field anti-ship and surface-to-air missiles that can be fired from hundreds of miles away. Large amphibs, their hovercraft and lumbering armored troop carriers that take hours to wade ashore and unload, would be punished by precision missiles, experts contend.

The Makin Island is one of the world's largest amphibs. But it's also considered a transitional vessel, with similar but superior high-tech "Big Deck Amphibs" like the San Diego-based America poised to share space in the piers.

The America, and up to 10 of its planned sister warships, will feature bigger fuel tanks and storage capacity along with hardened decks to support the F-35B Joint Strike Fighter, the next-generation aircraft that takes off and lands vertically. In other navies, those ships would be considered aircraft carriers — a point that has sparked questions about whether the Navy favors that capability over its traditional mission of putting Marines ashore.

"The answer, to me, is that we had better prepare to fight for command of the sea," said James Holmes, a professor of strategy at the U.S. Naval War College and a former Navy surface warfare officer who is widely considered one of the world's top experts on maritime battle. "As the greats of sea power tell us, you have to be able to win command of the sea if you want to use the sea to do things like conduct amphibious landings.

"So we need to be ready to do these things, but chances are there will be delays while we fight our way into the theater, reduce shore-based missile batteries and on and on. Sea power is no longer just about navies," he added.

Holmes believes the Marines might fret about the future of the amphibious fleet because ongoing studies have called for converting some assault ships into light aircraft carriers and replacing them with other vessels when they're retired, but the Navy must strike the right balance.

"As far as priorities, certainly the types of ships we need to defeat our enemies and take command of the sea must take precedence," he said, adding that it's "a lot easier to improvise a fleet of amphibious transports than it would to improvise destroyers or nuclear-powered attack submarines."

In a major war, like a potential Pacific-wide bout with China, the traditional mission of the amphibs likely wouldn't end.

Holmes said Marines could be called to seize islands, much as they did in World War II. Cancian added that the Corps also might return to traditional missions like coastal artillery batteries, working alongside the Army and other services to to defend anti-ship missile batteries on the islands and shoals peppering the Pacific Ocean.

That concept is still a work in progress.

"The bottom line is that there's no answer about the ultimate future of the ships and the marine expeditionary units, but we do know that in peacetime they're very useful," Cancian said. "You're seeing in the Middle East just how useful they are."