Next to a nuclear explosion, there is no more lethal killing force on earth than a big forest fire. The most violent are called “blowups” because they are capable of exploding. Just how they perform such a terrifying feat remains a mystery, but fire behavior experts think it has something to do with a convergence of weather patterns and hurricane force winds big fires often generate.

Fanned by such fearsome winds, flames become blast furnaces, then the furnaces explode. Trees that are not incinerated where they stand are often sucked from the ground and tossed hundreds of feet into the air. Only a handful of firefighters have survived a blowup, but from their accounts we know that blowups can outrun birds in flight, melt soil, boil stream water, crack open boulders, detonate old, pitch-filled trees like sticks of dynamite and incinerate entire mountainsides in seconds. Mercifully, most who fall before them suffocate before fire consumes their bodies.

Big forest fires have become the focal point in the West’s National Forest harvesting debate because harvesting— in this case restoration forestry—deals with the underlying cause of today’s blowups: vast stands of diseased, dying and dead trees. Whether still standing or lying in rubble, these stands are fueling some of the largest and deadliest forest fires ever to burn in the West. Environmental groups that oppose harvesting on principle say allowing dying forests to burn naturally is less harmful than logging. But new coalitions—whose members often live in or near at risk forests—see thinning as a way of slowing defusing an ecological time bomb. Most, but not all, forest scientists agree with them.

Over the last 50 years, two blowups have ended in great tragedy. Thirteen smokejumpers died in Mann Gulch in Montana, August 5, 1949. Then on July 6, 1994, fourteen firefighters died on Colorado’s Storm King Mountain. Norman Maclean (A River Runs Through It ) turned the Mann Gulch tragedy into his second great book: Young Men and Fire . Maclean marks as Stations of the Cross the final fiery moments in the lives of thirteen young men caught in a race they cannot win— moments Maclean marks as Stations of the Cross.

Maclean: “Dr. Hawkins, the physician who went in with the rescue crew the night the men were burned told me that, after the bodies had fallen, most of them had risen again, taken a few steps, and fallen again, this final time like pilgrims in prayer. When the fire struck their bodies, it blew their watches away. The two hands on a recovered watch had melted together at about four minutes to six. For them, that may be taken as the end of time.” Maclean again: “When Jansson, Roos and Sallee reached him, Sylvia was standing on a rock slanting heavily downhill. Hunched over and wobbling to keep his balance, he couldn’t stop talking. “Please don’t come around and look at my face; it’s awful.” Then he said, “Say, it didn’t take you fellows long to get here.” He thought it was about 5:00 in the morning.

Jansson pulled out his watch and said, “It’s 2:00 a.m. on the nose.” Then in his report, Jansson speaks to us. “Since his hands were burned to charred clubs, I peeled an orange and fed it to him section by section.” Sylvia said, “Say, fellows, I don’t think I’ll be able to walk out of here.” Jansson told him his walking days were over for the time being and he was “going to get a free ride out.” He tried to make this a joke, although it is hard to make jokes at night on a hillside that smells of burned flesh.”

Maclean spent almost 30 years trying to reconstruct a moment-by-moment account of what happened when Mann Gulch blew up. The result is one of the most vivid and meticulously crafted descriptions of a blowup ever written. “A fire can set up a whirling action by drawing the cooler and heavier air from the outside into the vacuum left by its own hotter and lighter air constantly rising and escaping,” he explained. “In case this seems like a theoretical and theatrical construction, you might go to your basement furnace when it is roaring and open its door, put your face in front of it, and feel the sudden alarm that you are about to be drawn into your own furnace.”

“Fire whirls both intensify existing fire and cause new fires,” he wrote. “Their rotating action is that of a giant vortex, and, as giants they can reach two thousand degrees in temperature. Fires that become giants are giant smoke rings with a downdraft in the center that is full of deadly gases and, what is more deadly still, heat so great that it has burned out much of the oxygen; the outer-ring is an updraft sometimes reaching the edge of the atmosphere. Some fire whirls, not all of them are flame-throwers. Some pick up burning cones and branches. Some of the giants pick up burning logs and toss them ahead, starting spot fires sometimes a long way ahead. When these spot fires unite, firefighters can be trapped between two fires.”

Firefighters were trapped between fires three times during the Great 1910 Fire, widely believed to be the largest forest fire in U.S. history: 86 perished. In two terrifying days and nights, a convergence of perhaps 1,000 fires raced across three million acres in northern Idaho and western Montana. The survivors told stories of almost unimaginable terror. Joe Halm, who held his crew at gunpoint to keep them from fleeing a fire he knew they could not outrun, described “a roaring furnace, a threatening hell.”

“The wind had risen to hurricane velocity,” Halm later recalled. “Fire was now all around us, banners of incandescent flames licked at the sky. Showers of large flaming branches were falling everywhere. The quiet of a few minutes before had become a horrible din. The hissing, roaring flames, the terrific crashing and rending of falling timber was deafening, terrifying. Men rushed back and forth trying to help. One giant, crazed with fear, broke and ran. I dashed after him, he came back, wild-eyed, crying hysterically. The fire had closed in and the heat became intolerable.”

On Big Creek, a tributary of northern Idaho’s St. Joe River, 30 men lost their lives while others lay prone for hours in the chilly waters of a tiny stream—great forest giants falling around and across them. A falling tree—in flames—crushed three men, while a fourth man—caught only by his foot—struggled to free himself. Men a few feet away heard his cries and prayers, but were powerless to help. “If the wind had changed, a single blast from the inferno would have wiped us out,” Halm said in a 1938 radio interview.

It was no better upriver. On Seltzer Creek, 29 died trying to outrun the inferno. And down-river, at Beauchamps’ cave, David Bailey saved himself by diving into a small creek. Fire burned his hands while he covered his head with them, but he lived to tell about it. Seven others on his crew were not so lucky. “They were cooked alive,” Bailey told an interviewer. “All of them tried to get at the very end of a small hole and they were piled up in an awful heap. When we tried to removed their bodies they fell apart.”

Ranger Ed Thenon described his crew’s brush with death on Moose Creek, two day’s walk south of the cave that became a grave. “Trees were crashing down all around us and the sight and sound of the fire was something terrible. The smoke lifted a little on the west side of the creek, and there, half-way up the mountain, was a whirlwind of fire just like a waterspout, only it was all fire and burning gas and a thousand feet high. It moved back and forth and up and down the slope, and the roar of it was like a million blowtorches. If it had ever moved down on us we would have gone out just like when you touch a candle flame to a mosquito.”

Eighteen members of Lee Hollingshed’s crew became Thenon’s mosquitoes. Panic-stricken, they took refuge in Henry Dittman’s cabin on Big Creek, only to have the cabin explode in flames. The roof collapsed and they were burned alive. Ed Pulaski’s crew was luckier. They huddled in a mine tunnel while Pulaski calmly hung wet blankets over the portal. “The men were in a panic of fear, some crying, some praying,” he later said. “Many of them fell unconscious from the terrible heat, smoke and fire gas. I, too, finally sank down unconscious.” The crew later walked and crawled into what was left of Wallace. “Our shoes were burned off our feet and our clothes were in parched rags.”

The nation was outraged, no one more so than Gifford Pinchot, then the (first) chief of the Forest Service, and a frequent critic of Congress’ failure to appropriate money for trail and road development.

“For want of a nail, the shoe was cast, the rider thrown, the battle lost,” he told a reporter from Everybody’s Magazine . “For want of trails the finest white pine forests in the United States were laid waste and scores of lives were lost. It is all loss, dead irretrievable loss, due to the pique, the bias, the bullheadedness of a knot of men who have sulked and planted their hulks in the way of appropriations for the protection and improvement of these national forests.”

In the decade that followed, the federal government, several state governments and the West’s major timberland owners joined forces to create a network of forest fire fighting cooperatives that still exists today. The government’s decision to “exclude fire” from western forests was widely supported by a public that had come to view forest fires as killers of both people and timber. It would be another 50 years before the ecological consequences of the decision began to surface.