PANAMA CITY, Fla. — Five years later, the scars of Hurricane Michael are still visible across Tyndall Air Force Base.

The snapped and jagged trunks of once-towering pines protrude across its 29,000 acres, leaving expansive views toward the Gulf of Mexico where thick forests once stood. Dusty, empty lots remain on the site of some of the hundreds of buildings that succumbed to the Category 5 storm in 2018.

But these days, what is most striking about life at Tyndall — home to roughly 3,500 employees and their families, including the 325th Fighter Wing, a key combat training force — is not what is gone, but rather what is emerging.

The daily soundtrack is one of bulldozers and backhoes, of whirring saws and spinning drills, of thousands of workers in hard hats bustling across the sprawling base. There are piles of sheetrock and electrical conduit, stacks of pipes large and small, mountains of metal duct work, prefab concrete slabs and sheet metal.

All of it is part of a $5 billion, roughly seven-year effort to rebuild one of the most strategically important bases in the nation, one that's also threatened by climate change. And not merely to rebuild it, but to construct what the U.S. military calls "the installation of the future," which will be able to withstand rising seas, stronger storms and other threats.

"What Michael did for us is, it wiped the slate clean," said Don Arias, a spokesman at Tyndall's Natural Disaster Recovery Office. "It gave us the opportunity to reimagine."

That reimagining includes elevating buildings above projected storm surges in coming decades, building housing units and aircraft hangars that can withstand fierce winds and enhancing the natural landscape to protect the peninsula where the base sits.

While the fixes are primarily geared toward making Tyndall more resilient for generations, another hope is that the lessons unfolding here can be replicated at other bases around the world that will face — or already are facing — similar threats.

"Tyndall becomes the test bed," said Col. Robert L. Bartlow Jr., chief of the Air Force Civil Engineer Center's Natural Disaster Recovery Division, which was created after Michael.

"We don't want Tyndall to be a one-off."

A chance to rebuild on a valuable location

Hurricane Michael was a monster.

The deadly storm barreled into the Florida Panhandle on Oct. 10, 2018, packing winds in excess of 160 miles per hour and fueling a catastrophic storm surge. The eye of the storm passed directly over Tyndall, where most service members and F-22 fighter jets had been evacuated.

The devastation left behind was staggering.

On the base alone, 484 buildings were destroyed or damaged beyond repair, according to the Air Force. The roofs of Tyndall's hangars, which housed some of the most expensive and high-tech airplanes in the nation, were shredded. Piles of rubble littered the base. The military eventually removed 792,450 cubic yards of debris — an amount that would fill the Capitol Rotunda nearly 17 times.

"I think 'biblical' is a fair word," Michael Dwyer, deputy chief of the Natural Disaster Recovery Division, said of the damage.

The disaster at Tyndall prompted fears in Florida that the Air Force might decide to shutter the base, which sits adjacent to badly damaged Panama City and contributes hundreds of millions of dollars a year to the local economy.

The military itself faced hard questions about whether to resurrect Tyndall — an endeavor that would cost billions of dollars, require years of disruption and still result in an installation perched on a vulnerable peninsula.

"A lot of people ask, 'Why rebuild?'" Col. Christian M. Bergholdt, commander of the 325th Operations Group, said on a recent morning at Tyndall.

He unfurled a map that shows the regions over the Gulf of Mexico where the Air Force trains pilots, including the use of live combat exercises. It's a massive area that encompasses 180,000 square miles of military-controlled airspace.

"This," he said, "is kind of a national treasure."

That ability to train over water and away from populated areas make Tyndall's location incredibly valuable to the Defense Department.

"It has unique military value that we cannot replace anywhere else," said Richard Kidd, who, before retiring at the end of May, was the deputy assistant secretary of defense for environment and energy resilience, overseeing the Pentagon's climate initiatives. "You can't pick that up and move it."

Given its prime real estate and historic importance, the military decided to take advantage of something it rarely gets these days — a blank slate.

The rebuild at Tyndall, which is expected to continue into 2027, marks the largest military construction project undertaken by the Pentagon.

"Think of it as the Air Force throwing its Costco card down on the table and buying buildings in bulk," Dwyer said of the massive undertaking.

A dizzying array of new technologies and approaches have been incorporated into the effort, from semiautonomous robot dogs patrolling the grounds to artificial intelligence software designed to detect and deter any armed person who enters the base. But the most robust funding is aimed at making Tyndall more efficient, connected and resilient in the face of a warming world.

Structures under construction — from dormitory complexes to a child care center to hangars that will house three new squadrons of the F-35A Lightning II later this year — are being built to withstand winds in excess of 165 mph. Steel frames, high-impact windows, concrete facades and roofing with additional bracing are among the features meant to weather the stronger storms to come.

At nearby Panama City, sea level rise has accelerated in recent years, with federal data showing seas have risen there more than 4 inches since 2010.

Planners factored in the potential for as much as 7 feet of sea level rise by the end of the century, and as a result placed the "vast majority" of new buildings at elevations that should be safe from storm surges for decades, Dwyer said. In addition, sensors placed near the low spots of buildings will send alerts the moment a flood threatens.

The Air Force also has created a "digital twin" of Tyndall — essentially, a virtual duplicate of the base that allows officials to simulate how roads, buildings and other infrastructure would hold up in different scenarios, such as a hurricane or historic rainfall events.

The job of protecting Tyndall, while largely a construction and engineering project, goes beyond just concrete and steel. The military also is determined to enhance the natural defenses that already exist along the base's dozens of miles of coastline.

On a sweltering spring afternoon, Gary Payne stood on the sugar-white beach along the Gulf of Mexico, stretching a hand far above his head to show how high the storm surge was from Michael.

"These dunes used to be 10 to 12 feet tall, but Michael pretty much flattened them," said Payne, the division's resilience coordinator.

Already, there are several projects planned around the base to help reduce coastal flood risks and erosion. Among them are efforts to restore dunes and sea grass meadows; the construction of a "living shoreline" composed of natural materials such as plants and rock and the installation of submerged oyster reef breakwater that can reduce wave energy and erosion.

"The nature-based components are really critical, because they are already there and already providing a benefit," said Christine Shepard, director of science for the Gulf of Mexico program at The Nature Conservancy, which is partnering with Tyndall on the resilience projects. "If you lose those habitats, you lose those benefits."

Shepard describes the military as an "early adopter" of such solutions. "The military has been appropriately considering sea level rise a lot longer than some other sectors," she said. "They know that the risk is real."

Payne agrees, and not just in the future. While leaders intend to scale up the nature-based projects over time, he is eager for any additional projection, as soon as possible.

"Even without [additional] sea level rise," he said, "the areas we are focusing on are already at risk today."

Making hard decisions 'before nature makes them for us'

As it faces more intense hurricanes and rapidly rising seas, Tyndall might be on the front lines of climate change. But it is hardly the only U.S. military installation grappling with the consequences of a warming planet.

"You have bases that are in every climate around the globe," said John Conger, director emeritus of the Center for Climate and Security and a former Defense Department official. "As the military looks at climate change, they look at it through the lens of mission. . . . It affects their ability to do their job."

Conger noted that U.S. installations exist on low-lying islands threatened by rising seas, in places such as Alaska and Greenland where permafrost is melting and sea ice is shrinking, in areas threatened by wildfires and extreme heat, saltwater intrusion and inland flooding.

The Pentagon long studied the potential impacts — it calls climate change " a critical national security threat and threat multiplier" — and has produced a growing body of research about the challenges, the potential solutions and increasingly specific plans to adapt.

The Defense Department maintains a web-based climate assessment tool, known as DCAT, that uses historical observations, global climate models and other data to help personnel plan for potential climate-fueled hazards at thousands of military outposts around the globe.

In addition, the Defense Department has spent years working on working on climate exposure assessments for major installations in the United States and abroad, though studies by the Government Accountability Office and even outside researchers have said work remains to make climate a key consideration throughout military planning.

Kate White, a DOD program director for climate and a veteran of the Army Corps of Engineers, said the military has a much better grasp than it once did of the "tough choices" that lie ahead.

"The department really has been thinking seriously the last few years of how to understand and plan for these future realities," White said.

But even when as the risks become more fully understood, policymakers will have to decide — as they have with Tyndall — what is worth defending, and how best to do that.

"There's not enough money in the DOD's budget to build a sea wall around all of our coastal installations," said Kidd. "Given that, the nation will be faced with hard choices. Right now, we are starting to prepare the analytics to support those hard choices when the day comes."

In many places, he believes, those choices might come sooner than later.

"We may be too late to make these hard decisions before nature makes them for us."

'This is really the test base'

Back at Tyndall, the rebuilding is entering a period known as "peak construction."

As many as 4,000 contractors are flocking to the base each day — plumbers, carpenters, electricians, welders — to work on the dozens of structures that are rising from the ashes of Michael.

New hangars for fighter jets, dormitories for service members, a housing facility for visitors, a child development center, a chapel, fire stations and a new headquarters building are each in various stages of construction.

A sense of urgency surrounds the hive of activity, even as it remains years from completion. After all, sea levels in the nearby Gulf are rising at a rapid clip; ocean temperatures are hotter than ever as another hurricane season arrives; torrential rains are becoming more common as warmer air holds more moisture.

Despite those threats, Bartlow, the chief of the Natural Disaster Recovery Division, feels optimistic about the base's long-term viability once construction winds down.

"I'm confident that if Tyndall were to experience another storm, a Category 5," he said, "the installation would survive largely intact."

But on this day, he and his team are monitoring potential damage at Andersen Air Force Base in Guam, where Typhoon Mawar is making landfall — the latest reminder that the threats at Tyndall are not unique, and that what the military learns here has implications around the planet.

"This really is the test base," Arias said. "This could very well set the standard."

The Washington Post's Chris Mooney contributed reporting from Washington.