Asked why his team wanted to climb Mount Everest, George Mallory apparently replied, "Because it is there." We go, he added, "because we can't help it. Or to state the matter rather differently, because we are mountaineers."

In the early 1920s, Mallory and his colleagues made three attempts, sponsored by England's Royal Geographical Society, to reach the summit of the world's highest mountain. The last one cost him his life.

In "Into the Silence," Wade Davis, author and explorer-in-residence for National Geographic, tells the story of the Everest expeditions. Richly detailed, and often riveting, with vivid portraits of all the players, his book juxtaposes human ambition, courage and adaptive capability with the relentless realities of terrain and weather. It will stand as the definitive treatment of this subject.

Many of the Everest adventurers, including Mallory, were veterans of World War I, an appallingly (and unnecessarily) destructive conflict. There was nothing more that death could show them, Mr. Davis writes, short of their own. By scaling the heights, these men sought to demonstrate to their tired and disillusioned countrymen (and to themselves) that the life of an individual "could still have meaning and that the war had not expunged everything heroic and inspired." Conquest of Everest might even provide a symbol of imperial redemption.

Mr. Davis demonstrates as well that the identity of the climbers as English gentlemen had an enormous impact on the expedition. By the 1920s, he indicates, it was clear that the debilitating effect of high altitudes (including life-threatening cerebral edemas) could be reduced with supplemental oxygen, delivered in steel bottles of compressed gas, and administered through a regulator and a mask. Nonetheless, traditionalists questioned whether use of the apparatus was "sporting." Appalled at the prospect of reaching the summit with faces covered in anonymity by devices "so powerfully evocative of the trenches," they mocked their more scientifically inclined mates, who considered carrying backpacks with oxygen no more artificial than wearing custom-made boots.

Snobbery, in fact, shaped the makeup of the Everest team. George Finch, the best ice climber in Britain and a strong supporter of oxygen, was excluded from two of the three expeditions because he was an Australian, had not attended the proper schools, had chosen a career in the sciences ("a profession unworthy of a gentleman") and did not bathe every day.

Embodying the prejudices of their day, the adventurers regarded the Tibetan porters they employed as filthy, ignorant and superstitious, and often treated them with condescension and contempt. Mallory proposed bringing one of them back to England to do scullery work, scrub floors, wait on tables, fetch and carry. Living in part of the cellar or a coal shed, he might after a while be accepted by his fellow servants: "he is a clean animal ... and not very dark skinned."

And yet, Mr. Davis suggests, the assault on Everest had a leveling effect on the mountaineers. At the end of the last expedition, he writes, the climbers built a memorial cairn, "a pyramid of small boulders rising higher than a man," with the names of all of the dead, Tibetans and Englishmen, inscribed. That night, they attended Rongbuk Monastery, and even though they couldn't understand a word, declared themselves impressed by the profound devotion of the lamas, who hitherto they had reviled.

In a campaign that mimicked World War I, one of them wrote, "Death had taken his toll from the best." For better and worse, heroes had been humbled.