One grew to a size larger than Rhode Island and levelled a Gold Rush-era town. Another swelled to a quarter of a million acres as it came within a few miles of Lake Tahoe. Another burned down 900 buildings and was the first-ever to reach 1 million acres.

In the past two years, California has found itself under siege from more large-scale fires burning with greater intensity than at any time on record. Giant blazes are tearing across the state with greater speed and frequency, destroying towns and sending smoke hurtling hundreds of miles away. Nine of California’s 20 largest fires have occurred since 2020, according to Cal Fire, the state’s firefighting agency. Four of them are still burning. The fires have forced state and federal officials to marshal armies of people and resources at all costs.

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In late August, New York Times journalists shadowed emergency crews in a remote forested area of Northern California as they battled the Dixie fire, which at nearly 1 million acres is the second-largest fire in state history. Over several weeks, the operation grew to a scale rarely seen before: Thousands of personnel were deployed, as well as hundreds of bulldozers, aircraft and other equipment, along with millions of gallons of water and flame retardant. Officials spent more than $610 million over three months to bring the fire under control — by far the most expensive suppression campaign in California history, according to the head of Cal Fire.

The Dixie fire shows that as wildfires have grown in size, so has the magnitude of the effort to combat them. But as government budgets become strained and extreme drought and the effects of climate change, alter the landscape, battling megafires — massive blazes that spread quickly and burn at high intensity — is increasingly costly, raising questions about the long-term sustainability of the firefight.

At the height of the operation, 6,579 people worked around the clock to battle the Dixie fire.

The command centre at the Lassen County Fairgrounds appeared like a small town that sprung up overnight. It was filled with offices in trailers, catering stations, fueling areas, laundry services, sleeping tents and parking spots for many of the 569 fire engines and 194 water trucks working Aug. 16, when the operation was at its peak.

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Each morning at 7 a.m., hundreds of firefighters, bulldozer operators and pilots gathered under a poplar grove for a daily briefing. Some crew members wore sweatshirts bearing the names of past big fires like badges of honour: Creek fire, Campfire, Lightning Complex. Dixie already had one, too.

In one area of the command centre, a resupply warehouse roughly the size of a Home Depot store serviced engine crews returning to the fire line. In another, volunteers with the California Conservation Corps rewound heaps of used 100-foot lengths of the yellow fire hose. In all, more than 1,174 miles of hose were used — enough to stretch from San Diego to Vancouver.

At the time, the Dixie fire, one of a growing number of wildfires that had broken out across the American West, spanned five counties, threatening nearby communities and spewing smoke into the atmosphere. Kristen Allison, a 25-year veteran firefighter who was stationed 70 miles away, struggled to comprehend the scale.

“Fifteen years ago, a 100,000-acre fire would be the largest fire of your career. Now, we have 1-million-acre fires,” Allison said. “We’re the size of Rhode Island, working toward Delaware.”

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“Meanwhile, there are five other 100,000-acre fires burning right now in Northern California,” Allison added. “Even if we had all the resources we wanted, we would not be able to contain these fires.”

At the fire’s peak, 198 bulldozers worked to contain it, helping cut 1,792 miles of fire breaks.

Much of the fight against the Dixie fire was a gruelling and dirty effort to head off future burn: As many as 89 hand crews on a single day burned ground cover and carved so-called line breaks — barriers to slow or stop the progress — through the forest. Bulldozers, many of which were operated by contractors for upward of $7,000 a day, cleared wide swaths of trees and flammable vegetation. Strike crews laid those dozer lines with fire hose and stood guard, often through the night, to prevent the fire from jumping over.

Fueled by a combination of high winds, mountainous terrain and dry conditions, Dixie shows how the scale of wildfires has dramatically increased. In 2010, 72,000 fires in the United States burned 3.4 million acres; last year, 59,000 fires burned 10.1 million acres, according to the National Interagency Fire Center.

Trying to put out Dixie sometimes felt like an exercise in futility. It routinely leapt over breaks, and a team led by Sarah Collemer, a Cal Fire equipment boss from Santa Cruz, worked to clear them.

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“We’ve been trying to hold the line, but the wind keeps coming up, and most of the embers start a new fire,” Collemer, who was overseeing a team of 30 bulldozers, said. “It’s just hard to start over every day on the line.”

Like other recent megafires, the Dixie blaze has burned at a severe pace, sometimes scorching 50,000 acres in a sustained run over 8 miles in one day.

Crews used enough fire retardant to fill 31 Olympic-size swimming pools.

Air attack — deploying planes and helicopters to drop water and retardant — is often the costliest part of any large wildfire operation.

Aircraft have dropped about 21 million gallons of flame retardant mixture on the Dixie fire, at a cost of $4.62 per gallon. The aircraft themselves cost more than $1 million a day in the initial weeks of the fire.

“They call me the most expensive man on the fire,” said Matt Stanford, the air operation branch director at Cal Fire base camp. “Every day, costs come in, and I’m on the top of the heap.”

Some critics argue that retardant, a mixture of water and phosphate salts often used as a fertilizer, does more damage than good. The U.S. Forest Service restricts use around waterways to avoid fish kills and algae blooms.

Despite the trade-offs, air attacks are the most visible show of force and can cover lots of ground quickly. The candy-colored liquid retardant lingers long after water has evaporated and is more effective at lowering a fire’s intensity so that crews can engage on the ground.

When the smoke thickens, planes are grounded, forcing aviation chiefs to use large helicopters that can fly under the smoke — though they hold smaller quantities of water or retardant. Under heavy smoke conditions, helicopters, too, are grounded.

Crews were diverted even as the fire still raged.

Even before the Dixie fire was close to contained, Cal Fire began diverting resources from it. While crews were using drip torches to burn off dry ground cover that could feed oncoming flames, some personnel were reassigned to the Caldor fire, which was racing up the Sierra Nevada mountains toward South Lake Tahoe, one of California’s premier tourist destinations.

The Caldor fire stopped within just a few hundred meters of South Lake Tahoe, and the town was spared.

California pays for large wildfire responses through an emergency fund with no set limit on spending. In recent decades, the percentage of the U.S. Forest Service budget spent on wildfires increased to 50% from 20%, and in 2021 the Forest Service received a $2 billion budget for wildfires. State and federal officials threw every resource possible at both megafires.

Thom Porter, who leads Cal Fire, said he supports more wildfire prevention strategies but that the reality during this high fire season doesn’t allow for it.

“The efforts that we put in are absolutely necessary,” Porter said. “There is no choice but to fight a fire when the fire is going. We’re seeing entire centers of towns burn up, historic centers of towns, like Greenville,” he added, referring to the city that burned.

Since July, California has spent $1.1 billion trying to put out fires.

President Joe Biden, who has called wildfires “a blinking code red for our nation,” has made fire suppression a priority of his infrastructure bill, pledging to increase federal funding and military assistance. During a joint conference with Gov. Gavin Newsom in September, the president said the bipartisan bill would include $8 billion for wildfire resilience and promised to provide California with “every resource available to keep families safe.”

“It’s a great starting point,” Porter said, adding that he welcomed more investment by the federal government while acknowledging that it’s impossible to put out megafires under certain weather conditions, no matter the amount of firefighters and flame retardant.

As of Sunday, fires had burned more than 2.8 million acres across the state. The end of fire season is still weeks away.