YOSEMITE NATIONAL PARK, Calif. — Each afternoon the fire's thunderous plume rose.
At night, helicopter crews at the Crane Flat lookout watched a line of orange burning across the horizon. The line kept drawing closer.
By the last week of August, every effort to halt the Rim fire before it moved deeper into the national park had failed. The blaze now had a clear path to the Tuolumne and Merced groves of giant sequoia, and the Rockefeller grove, one of the last stands of giant sugar pine untouched by logging.
On Aug. 30, a Friday, a group of firefighters gathered at the lookout to launch a risky plan to protect some of Earth's oldest and largest living organisms.
Even Ben Jacobs, the division commander, was nervous.
Jacobs, 55, had fought wildfires and managed prescribed burns at Sequoia Kings Canyon National Park. But he had seen crews take chances earlier in the week trying to save family camps and businesses. If they'd gambled for buildings, what would they do for living giants?
He also worried that if crews lost control of the backfires they were about to ignite, flames could spread for miles, even as far as the Merced River, west of the park's famous valley.
"Listen," he said. "Nobody wants to be the guy who burned down Yosemite."
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They had known a fire like this was coming.
A hundred years of fire suppression had created a buildup of trees, logs and other fuels. Fire could climb up and fly through the crowns of trees rather than burn on the ground as forest fires had for centuries. Add two years of extreme drought, and the Sierra Nevada was a pile of kindling.
Inside Yosemite, officials had tried to restore the natural cycle of fire. For 40 years, lightning-sparked flames in wilderness areas had been left to burn, and specialists lighted controlled burns near tourist areas. But that might not offer enough protection.
"Hypothetically those old fire scars would slow the fire the further it moved into the park," said Gus Smith, Yosemite's fire ecologist. "But the Rim fire was like a flood, and it was coming. This was not the fire you wanted to test out a hypothesis."
It had first been spotted in a remote area of neighboring Stanislaus National Forest.
Two days later, on Aug. 17, flames exploded over a ridge above the Tuolumne River. Whitewater rafters navigating the canyon of buckeyes and bald eagles said it sounded like bombs.
It was about 20 miles in the distance, but Yosemite Fire Chief Kelly Martin, a specialist in predicting fire behavior, knew it was headed their way.
"This is it," she said. "This is the Big One."
Now, it had pushed 30 miles inside the park, moving south toward California 120 — the main east-west route through Yosemite. In one day it had burned 50,000 acres inside the park. The biggest fire since the park began keeping records in 1930 had burned 46,000.
The sequoias evolved to face wildfire. But officials feared that this fire could kill even trees that had been shrugging off flames since before Rome burned.
Jacobs and Taro Pusina, Yosemite's deputy fire chief, drew up a plan. They would set three coordinated backfires and try to stop the wildfire with a "catcher's mitt" of charred earth.
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