ABOARD THE USS BONHOMME RICHARD (AP) — After three tours in the deserts of Iraq, Lt. Col. Joe Levreault says he felt a bit rusty when he climbed into the helicopter to do what he was trained to do best as a Marine pilot — fly troops from the ship to the shore, even under fire.

But he quickly got back into his groove and was more than ready to carry out his mission Friday when thousands of sailors and Marines will carry out the largest amphibious landing exercise on the West coast since the Sept. 11 terror attacks sent troops to wars in landlocked regions.

The Marines and sailors are aboard the 844-foot USS Bonhomme Richard off the coast of Southern California, preparing to storm the beach.

Marines say the training that kicked off May 24 has reinvigorated them by bringing them back to their roots as "soldiers of the sea." Some say the heavy fighting in Iraq and Afghanistan in the last decade has relegated them to the status of a kind of second land army.

"After so many years away, your skills always diminish and any time you can get back to the boat, it's good," said Levreault, 40, who has served for 18 years. "It's our bread and butter."

The exercise comes at a pivotal point for the Marines who are facing questions from Defense Secretary Robert Gates about whether major amphibious landings that made the Marine Corps so famous worldwide are becoming outdated in today's warfare.

Defense analysts accuse a cost-cutting Gates of trying to dismiss the value of beach landings and the needed equipment, like a $13.2 billion plan to buy large numbers of the Expeditionary Fighting Vehicle starting in 2012. The amphibious vehicles, also known as EVFs, help get troops from ship to shore while under fire and mark a significant upgrade over the current technology available to the military.

Gates is scrutinizing every aspect of the military in his search for roughly $10 billion in annual savings to sustain the combat force and invest in its modernization.

"The United States' Marine Corps has been conducting amphibious operations for 200 years. It's a unique capability and there is no analytical basis for arguing that capability won't be needed in the future," said Loren Thompson, a defense analyst for the Lexington Institute. "Everyone we are likely to fight in the future is going to be close to the sea ... like Iran, like North Korea, like Vietnam, like almost any place you can mention other than Afghanistan."

And he added: "If the EFV is canceled, many marines will die in the future for lack of an adequate vehicle."

Called "Dawn Blitz," the Camp Pendleton exercise kicked off May 24 and will culminate Friday when troops reach the Camp Pendleton beach on 60 Amphibious Assault Vehicles — seafaring tanks supported by 16 hovercrafts and seven amphibious ships.

It will wrap up two days before the 66th anniversary of D-Day — the world's largest amphibious invasion of all time. More than 160,000 troops landed along a 50-mile stretch of the Normandy coast on June 6, 1944, paving the way for the Allied victory.

Defense experts say the lessons learned that day still apply.

The Marine Corps says the exercise with the Navy makes an agile force capable of doing everything from assaulting an enemy beachhead to bringing food and supplies ashore to a disaster-stricken nation such as Haiti. Outgoing Commandant Gen. James Conway wants his "soldiers of the sea" to get back to their roots.

About 2,000 Marines and sailors were aboard the USS Bonhomme Richard, whose primary mission is to embark and deploy troops in amphibious assault operations by helicopter, landing craft and seafaring tanks. Camp Pendleton spokesman Capt. Mike Alvarez said the exercise is allowing Marines and sailors to work together side-by-side in a way that they have not been able to do since 2001.

Navy spokesman Lt. Kyle Raines said many of the Marines participating in the exercise this week had not done a landing from sea before this drill. "It is a competency we need to maintain."

Gates has suggested that the military has overstated its requirements in a post-Cold War world and that Congress is unlikely to give the Pentagon the sizable budget increases it has enjoyed since 2001. The current defense budget, not counting the cost of fighting in Iraq and Afghanistan, is $535 billion; the administration is asking for $549 billion for 2011.

Gates managed to get Congress to agree last year to stop production of the Air Force's F-22 stealth fighter earlier than previously planned, and he halted an Army ground combat vehicle project that had been a top priority.

Gates has also asked the U.S. Navy why it needs 11 aircraft carrier strike groups when no other country has more than one.

Defense analyst James Carafano of the Heritage Foundation said the United States cannot take its military strength for granted.

"Gates has got the brilliant idea that we can waltz in everywhere we go. You know what? The enemies are not going to let us into the ports and we're going to be sitting there like in the 1920s, rowing ashore with a row boat," he said. "I think Gates is incredibly short sighted. The Marines are not idiots. They are not doing this simply because they have always done this. We are a great power, but if you don't have amphibious capabilities, you are not a great power anymore."