In the Philippine Sea (CNN) One hundred twenty years ago this month, US Navy Commodore George Dewey led a squadron of warships from Hong Kong and steamed towards the Spanish colony of the Philippines. It was the start of the Spanish-American War.

In Manila Bay on May 1, Dewey's ships smashed the entire Spanish fleet while suffering only a handful of US casualties. That crushing naval victory cemented the US as a major player in the Pacific Ocean, leading to nearly a half century of US colonization of the Philippines.

It also turned Dewey into a war hero. He continues to be the only US naval officer to have attained the rank of Admiral of the Navy.

More than a century later, a US guided missile destroyer proudly carrying Dewey's name continues to patrol the waters of the Pacific Ocean, projecting US naval power into this sprawling region.

The Navy gave CNN access to the USS Dewey during exercises last month. A US Navy MH-60S Knighthawk helicopter picked our team up from White Beach Naval Station on the Japanese island of Okinawa for the journey to the 510-foot-long, 9,000-ton warship.

Roughly 20 minutes after lift-off, we landed safely and smoothly on the back deck of the destroyer as it churned through the Philippine Sea.

Once on board, officers led us to Dewey's ceremonial sword, which is stored in a glass case near his portrait in the ship's state room.

Threats from North Korea

Though it sails out of San Diego, California, the Dewey is currently assigned to an expeditionary strike group led by the USS Wasp, now operating out of Japan.

This fighting force, comprised of four ships, roughly 4,000 sailors and Marines, as well as helicopters, Osprey vertical takeoff and landing aircraft, and F-35 stealth fighter jets, is scheduled to participate in annual joint military exercises in South Korea in the coming weeks.

JUST WATCHED CNN gets access to latest F-35 Lightning jet Replay More Videos ... MUST WATCH CNN gets access to latest F-35 Lightning jet 03:16

Naval commanders are reluctant to discuss that assignment, in part because of recent dramatic policy shifts in the Trump administration's approach to North Korea.

After a China-North Korea summit in Beijing, President Trump tweeted kind words about the North Korean leader, writing "now there is a good chance that Kim Jong Un will do what is right for his people and for humanity. Look forward to our meeting."

But last November, Washington was engaged in serious saber-rattling, dispatching three aircraft carriers to simultaneously patrol off the coast of Korea for the first time in a decade, part of a clear effort to convince Pyongyang to give up its nuclear weapons tests and ballistic missile launches.

In 2017, North Korea launched a total of 23 missiles. Two flew over Japan. Pyongyang also threatened to shoot a salvo of missiles at Guam to hit the US island with "enveloping fire."

Ships like the Dewey are meant to be part of a first line of defense against such threats. The Dewey is armed with the Aegis weapons system, which can detect incoming threats, like missiles, and share the information with other warships.

Other destroyers specifically equipped with ballistic missile defense can then theoretically shoot down a weapon fired from North Korea.

But throughout last year's barrage of North Korean missiles, the US Navy's Aegis missile defense never launched its interceptors.

"In those particular cases, there was a determination that there wasn't a specific threat on any specific population," said Rear Adm. Brad Cooper, commander of the amphibious force of the Navy's 7th Fleet.

"More importantly, the capability does exist with the platform to defend against ballistic missile attack."

Live-fire drills

During our visit to the Dewey, the crew performed a series of live-fire drills, where the sailors discharged short-range 50-caliber guns, a long-range 5-inch gun, and two other machine guns.

One of those machine guns and the Close-in Weapon System -- a Gatling gun designed to shoot down incoming missiles -- both jammed during the exercise, a reminder of how important the drills are to iron out kinks to make the vessel combat-ready.

Cmdr. Anthony Webber, commanding officer of the USS Dewey, says the training is also important to improve the skills and camaraderie of the crew numbering about 325 members.

The USS Dewey fires its 5 inch gun during a training exercise in March 2018.

"My sailors love firing weapons, they love the practice, they love the training, and it gets them riled up, prepared," Webber said. "It keeps them in a mindset of knowing that we could potentially have to use these weapons someday."

The Dewey also has a battery of missile pods on its forward deck, armed with Tomahawk missiles, Standard missiles and anti-submarine rockets.

This type of firepower, Webber said, sends a message of support to US allies in the region, and a warning to potential enemies.

"It shows that we've been operating in these waters for decades, it shows that the US still has a vested interest in this region, and that we're here to continue to protect the sea lanes, and make sure that the waterways remain free of any type of adversaries."

South China Sea

This is the argument the US government uses to justify its "Freedom of Navigation Operations" in the South China Sea.

While a nuclear-armed North Korea poses an immediate threat in the Asia Pacific region, China presents a longer-term challenge to US dominance of the region.

For years, China has been constructing and fortifying man-made islands throughout the South China Sea.

Beijing claims almost all of this body of water as its own, despite objections from more than a half dozen other countries with coasts along the South China Sea.

In May 2017, the Dewey was sent to skirt by one of China's man-made islands.

JUST WATCHED US destroyer in South China Sea Replay More Videos ... MUST WATCH US destroyer in South China Sea 01:24

It sailed within 12 miles (20 kilometers) of Mischief Reef, in the Spratly Island chain, prompting condemnation from the Chinese Defense Ministry.

"Freedom of navigation is always on the burn," Webber said. "It's one of the tenets and one of the missions we're expected to conduct."

Collisions at sea

Amid challenges from China and North Korea, the US Navy in the Pacific has struggled with major setbacks within its own ranks.

Last year, two other guided missile destroyers -- the USS Fitzgerald and the USS John McCain -- suffered fatal collisions with merchant ships leaving 17 US sailors dead.

Three other US warships either ran aground or suffered non-fatal collisions with civilian vessels in 2017 in the Pacific.

In response, the Navy fired a series of top officers including -- for the first time -- the vice admiral who was commander of the 7th fleet.

The Navy says it has implemented procedures to bring an end to these accidents at sea.

"We've taken the necessary precautions, we've received guidance from our headquarters as far as how to safely navigate the ship...and also provide training for our sailors," Webber said.

US dominance in the Pacific

The sun is setting over the Philippine Sea as our helicopter lifts off from the back deck of the USS Dewey.

One hundred twenty years after the Commodore Dewey crushed the Spanish in Manila Bay, the US still commands the most powerful navy in the Pacific.

Now the US is the deeply-entrenched force in the region, being challenged by a rising China and its North Korean ally.

Navy commanders insist the US is here to stay.

"For our allies and regional partners, we continue to remain deeply committed to our friends...not just in words but in meaningful action," said Rear Adm. Cooper.

"For our potential enemy, we now bring more lethality to bear, and we're exercising this capability more and more each and every day."