WE WERE MARCHING up a strip of shattered rock laid out between two streams of the purest white, frozen highways extending in great ripples toward the head of the Siachen Glacier—the largest alpine glacier on earth, nearly two trillion cubic feet of ice. The air was frigid and the light crackled with the crystalline clarity found only above 16,000 feet. The sky was an unusually deep blue—a blue that bordered on violet, a violet that shaded into black, a black that warned of cold that could snap bones and stop the dance of molecules dead in its tracks.

Up ahead rose a snowy 18,950-foot saddle that marked the end of the Indian subcontinent and the beginning of Central Asia. From its crest you could gaze into India, Pakistan, China, and Tibet. Surrounding us on all sides was an unbroken wall of pinnacles—huge cetacean humps barnacled with impossibly large cornices, seracs, and needlelike spires. "I am so happy to be in these mountains!" cried Mohmad Yaseen Khan, a 47-year-old Kashmiri Muslim who was serving as our guide and cook. "The number of peaks I want to climb here is... is... well, I will have to make a special trip back just to count them. See how each one shines in a different way? See how their shapes are different? This is a place where a mountaineer would want to be buried."

Within a 25-mile radius of where we stood, 48 peaks rose above 19,000 feet; only 16 of these have names, and only six have been climbed. Above them towered 27 giants with altitudes exceeding 23,000 feet. Thirteen of these have never been scaled, and they include some of the greatest remaining prizes in Himalayan mountaineering: Saltoro Kangri II, four peaks in the Apsarasas group, and another three in the Teram Kangri group.

But there's a reason these mountains remain untouched: They sit in the middle of a 250-square-mile war zone where India and Pakistan have been fighting for the past 19 years as part of their intractable dispute over the state of Kashmir. What might be a climber's paradise is instead the site of a harrowing and improbable siege, the highest and coldest combat theater in the history of the world.

For four days, Yaseen and I, along with photographer Teru Kuwayama and 11 Ladakhi porters, had slogged up the middle of the glacier, ascending through a series of Indian army camps, toward a place called Kumar Base, a bleak outpost at 16,000 feet that serves as the central supply depot for two battalions of Indian troops. Daily artillery barrages and small infantry skirmishes occasionally mushroom into full battles, but for most of this war, India and Pakistan have been mired on the ice, burning up huge amounts of resources and manpower to hold the lines at heights that reach 22,000 feet.

At Kumar Base, the by-products of this stalemate were glaringly apparent. The camp is a cluster of 20 fiberglass huts and tents shared by some 35 officers, enlisted men, and porters. Perched on the crest of a massive, scabrous pile of reddish-brown rubble roughly 60 feet high and 900 feet long, it has the same features as the surrounding mountains—cols, ridges, arêtes—with one significant difference: It's made of garbage.

We picked our way through the scab with the kind of care normally reserved for a high Himalayan traverse. At the base of the camp, a recent avalanche had disgorged burlap sacks, old door frames, mortar boxes, rolls of bailing wire, and pieces of fiberglass. Running down the flanks were chutes filled with an unstable layer of plastic sunscreen bottles, bent stovepipes, charred wood, helicopter wheels, and rotting vegetables. As we trudged toward the summit, precarious cornices threatened to crack off and bury us in a deluge of empty jerry cans, burst oil drums, tattered parachutes, ammunition cases, crushed cartons of mango juice, box upon box of two-minute masala noodles, and large metal containers labeled ANTI-PERSONNEL MINES.

All of the other camps we'd passed through were miniature versions of Kumar, and their collective filth—a dietary and industrial record of nearly two decades of uninterrupted war—was bound for the same destination: the bowels of the glacier. From there, this toxic compost would leach into the headwaters of the Nubra River, and then into the Shyok River, the Indus River, and ultimately into the Arabian Sea.