(CNN) Five minutes before six, when the first glow of dawn has barely touched the horizon over the Pacific Ocean, the power guitar chords of a song by the band Three Doors Down suddenly crackles to life over the ship's loudspeakers.

Every morning, the executive officer of the USS Ashland plays a different tune to start the day at sea.

Moments later, light floods the narrow hallways, steel airlocks, and steep stairwells of this warship.

Sailors and Marines clamber out of claustrophobic, packed bunks, splash water on their faces, and line up patiently outside the ship's mess.

Inside, Navy cooks dish up pancakes, eggs, fruit and endless cups of steaming coffee.

'Taming a dragon'

This month, the US Navy and Marine Corps provided CNN exclusive access to Exercise Blue Chromite 18, the latest in an annual series of military exercises conducted on the Japanese island of Okinawa.

To reach the Ashland, visitors board a vessel called a Landing Craft Utility, or LCU. This open air ship can ferry tanks, bulldozers or hundreds of troops across open ocean.

On our recent journey, the LCU pounded through stomach-churning, eight-foot waves that crashed over the ship's bow.

On approach to the Ashland, the much larger warship slowly opens enormous doors in its stern.

At that point, the smaller boat churns forward, into the flooded belly of the Ashland. Barking orders, dozens of sailors pull enormous ropes in an effort to stabilize the rocking landing craft.

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"It's like taming a dragon," says Ensign Vanessa Nicolle, a public affairs officer aboard the USS Ashland.

Floating city

To civilian visitors, the USS Ashland can feel like a small floating military city.

During a recent overnight visit by CNN, the vessel carried a crew of 340 sailors, as well as 290 Marines.

Technically classified an amphibious dock landing ship, the Ashland has its own engineering department, a gym where service men and women pump iron, a small fleet of skiffs and motor boats, and a helicopter pad.

Its most impressive feature is the cavernous well deck, deep in the bowels of the vessel.

This water-borne garage can park dozens of vehicles ranging from bulldozers and trucks to humvees and tanks.

From platforms like this, the US armed forces can project military might on land, sea and air around the world.

The Ashland seen from a Landing Craft Utility (LCU).

Promotion at sea

On Wednesday, Marines from the 1st Battalion, 3rd Marine regiment lined up in formation on the helicopter deck of the ship for a solemn ceremony.

They were promoting Lt. Jesse Schmitt of Palm Beach, Florida, to the rank of captain. It is a major milestone in the career of any officer.

Lt. Jesse Schmitt of Palm Beach, Florida, is promoted to the rank of captain during a ceremony on the Ashland's deck.

"I, Jesse Schmitt, do solemnly swear that I will support and defend the Constitution of the United States of America," the new captain says, standing in front of a red Marine Corps flag held aloft for the occasion.

In a short speech, the unit commander lamented that Schmitt's wife couldn't attend the ceremony.

"The sad part about being a Marine and part of our naval force is that we're frequently deployed away from our families," said Lt. Col. Jeremiah Salame.

"But the rest of his family, our Marine Corps, is here to support him."

Deadly maritime accidents

The US commands the world's largest navy.

But the service was rocked by two deadly collisions last summer which the Navy ruled were "avoidable."

The incidents served as a tragic wake-up call.

"If you start to feel too overconfident... that's when something can happen," explains Cmdr. Steve Wasson, the commanding officer of the USS Ashland.

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In response to the accidents, the Navy fired eight senior officers. Aboard the Ashland, officers say they also had to undergo new training and adopt additional measures to prevent future possible collisions.

"One thing that the Seventh Fleet has done is take an operational pause and kind of just readdressed back-to-basics, basic watch-standing and communications and procedural compliance and forceful back-up," Wasson says.

"To not have one single point of failure is critical."

Responsibility heavy on young shoulders

At sunset on the bridge deck of the USS Ashland, more than a dozen junior officers take turns scanning the horizon both with binoculars and with control panels and computer screens in the ship's glassed-in pilot house.

Most of the officers here are in their 20s, with only a few years' experience in the Navy.

"We're responsible for the lives of the crew," says Lt. John C Michelek, a Buffalo, New York, native who has been in service for two years.

That message is hammered home at 10 p.m. By that time, the ship has gone mostly dark and the lights in the corridors and on the computer screens in the pilot house turn a ghostly red as a security measure. In the dim ruby light, the ship's chaplain, US Navy Lt. Jonathan Maruszewski, reads a prayer over the loudspeakers.

The prayers, which allow a rare moment for quiet and contemplation, are all the more poignant for the service men and women who have lost their friends and colleagues in the fatal accidents at sea in the past few months.

Amphibious Landing Drill

On Thursday morning, all hands are on deck to prepare for the main event of the Blue Chromite 18 drills -- a simulated invasion of the military-owned Kin Blue Beach in Okinawa.

After a hearty breakfast before sunrise, the Marines head below deck to prepare their weapons and kit, and smear camouflage paint on their faces.

Marines prepare for the commencement of the Blue Chromite 18 drills.

Lining up in formation, the Marines then file into a dozen amphibious assault vehicles (AAVs) -- tanks which can move between land and sea.

The sailors begin a process of slowly releasing water into the well deck of the ship by hinging open the stern doors, turning it from an underground car park to a flooded mobile port within minutes.

At 8:40 a.m., an advance team departs the warship on board a landing craft utility, to take part in the land-based drills.

Next, the AAVs roar into life and smash into the swirling sea.

Within an hour, they have traveled around four nautical miles through the ocean and are steaming up to the beach through sparkling turquoise water.

It's an impressive and somewhat menacing sight.

Troops prticipate in a simulated beach landing.

To prevent alarm among the local population, a text message alert with a special alarm was sent out around Okinawa a day earlier, to warn local residents and tourists that a military drill would be taking place.

On arrival at the beach, the back doors of the floating tanks flip open and the marines explode out onto the sand, running towards the beach wall to line up on the ground with their guns in combat-ready position.

Then the land and air drills begin, coordinating around 2,500 troops in a mock assault on the beach and in the surrounding jungle, with multiple military helicopters providing aerial support.

The drill provides a chance for junior and experienced officers to put their training to the test.

This sort of exercise is essential to keep America's fighting force ready for anything, says Col. Kevin Norton, commanding officer for the Marines.

"If called upon we can respond to any crisis across the range of military operations," he tells CNN. "The message is we're ready and capable, and we're training to execute any military operation we're called upon to do within the region."

Guarantor of stability?

Since World War II, the US has been the preeminent military power in the vast Asia Pacific region.

Washington has maintained that position with an elaborate network of alliances, such as the one that allows the US to station some 50,000 troops in bases across Japan, including the island of Okinawa.

"There are well over 22 countries in the Pacific, that are friends and allies, training, working together," says Norton. "And that network quite frankly provides stability and security throughout the entire Pacific."

But the US position in the region is being challenged. North Korea continues to flout international conventions by conducting nuclear weapons tests and firing intercontinental ballistic missiles which are banned by multiple United Nations Security Council Resolutions. And China's economic and military advances have grown to put the Communist country on par with the US.

President Donald Trump was elected in 2016 after promising to recalibrate America's international alliances to make them more beneficial to the US.

With his Make America Great Again platform, it is not clear whether the US can or wants to continue playing the leading role on this side of the world.