“My body just failed me,” he said, as he drove past the white ash of homes he had tried to save that night.

Fighting wildfires has always been draining, dangerous work, but firefighters say they now are being flung from one huge blaze to the next, using the same old axes and scrapers to fight a new species of mega-fires born from years of drought, while dealing with rising temperatures and government policies that filled the woods with tinder. Fire seasons that once ran from May to September can now stretch to Christmas.

Even with 29,000 firefighters working across the West, officials had to call up the National Guard and active-duty troops this year to supplement. Residents have pitched in. Fire officials are letting some blazes burn, keeping crews and equipment on fires that threaten lives or homes. And firefighters say they are working at a furious pace to keep up.

“There are no fresh bodies coming to work because everyone is at work,” said Mike Lopez, the president of the union that represents firefighters with California’s state fire agency, commonly known as Cal Fire.