"Obviously, I don't have to worry about losing my feet to the cold," said Stephen Martin, who calls himself a desert rat from suburban Phoenix who hates being cold. "I've already lost my feet. I don't want to lose my hands to frostbite."
Martin and one other member of the expedition are double amputees.
Another fear for Martin is that a prosthetic leg might break in the unforgiving conditions. "I brought a spare pair of feet," said the retired Army corporal who went back to Afghanistan as a contractor. He was injured by a roadside bomb. Martin returned to Phoenix and tried for 14 months to save his legs before undergoing amputation in November 2009.
The team says the climb is not only for them, but for others severely wounded in wars, including those to follow.
"We want to show in this project ... how active and how independent these wounded warriors can be, even with very severe injuries," said Kirk Bauer, climber and executive director of Disabled Sports USA, the group behind the climb with its Warfighter Sports program.
Bauer, a retired Army sergeant who lives in Baltimore, lost his left leg above the knee to a grenade in Vietnam.
The climb is also a fundraiser to help the organization raise money to help other wounded soldiers.
The climbers are scaling McKinley with crampons, climbing poles and ice axes to find firm footing on ice. They're moving single file, tethered to each other by rope, each carrying a heavy backpack of supplies and taking turns pulling a sled with more gear.
Besides narrow, treacherous paths, they will have to contend with potential blizzards, winds that can reach 100 mph, glaring heat during the day and frigid nights. They're navigating razor-thin ridges while also having to keep an eye upward for falling rock.
These climbers face additional challenges, including maintaining their energy with their carbon and fiber prosthetics they use more. They're concerned about abrasions where their skin meets the prosthetic and about how the artificial limbs will react to the cold. The above-the-knee amputees also must worry about solar charges for batteries that power the prosthetic knee unit computer, which ensures the knee doesn't buckle.
"If something happens there the leg stiffens up and we become like Peg Leg Pete climbing the mountain, so it's going to be much more difficult," Bauer said.
Others coming back from Afghanistan may be inspired, he said, and know that despite their injuries they can be active and productive and can lead full and healthy lives.
Ret. Army Capt. Jesse Acosta has all his limbs, but the Austin, Texas, native now working on Wall Street sustained permanent damage to his hip, leg, arm and back from a roadside bomb in Iraq.
He said the climb is meant "not only to prove to ourselves just what is (possible) given our own limitations, but hopefully and probably more importantly, inspire in others ... that this is very much an obstacle which can be overcome."
The climb started June 11, and as was expected climbing with prosthetics, it's been a slow slog. Daily short updates via satellite phone are posted on the Internet, provided by either the climbers or members of their guiding group, Mountain Trip. The group spent three days at 11,200 feet, first to rest and then wait out a snowstorm and high winds. They've so far reported no problems.
If all goes according to plan, they hope to summit the mountain on June 28, and are scheduled to fly home July 3.
But success is far from guaranteed.
The park service says 1,191 people have registered to climb Mount McKinley this year. Of those, 795 have completed their attempts, with 295 people or 37 percent making the summit. There are 283 people currently climbing the mountain.
So far this summer, six people have died on McKinley. Four of those deaths occurred last week when an avalanche caught a team of five Japanese climbers, pushing them into a 100-foot crevasse. One member was able to climb out.
The wounded warriors learned of the deaths, and posted this on their website Saturday: "Thoughts & prayers to the Miyagi Workers Alpine Fed. Expedition."
The combat veterans were chosen for the climb because of their attitude, their mental and physical fitness and the desire to improve themselves, Bauer said.
The group went through six months of training before the ascent attempt. Three climbers Bauer, Acosta and Ret. Army Sgt. Neil Duncan of Denver, the other double amputee previously climbed Tanzania's 19,336-foot Mount Kilimanjaro.
If successful, they wouldn't be the first with physical challenges to make the ascent on Mount McKinley, also known as Denali, an Alaska Native tribal word meaning "the great one."
According to statistics provided by Denali National Park and Preserve, Sarah Doherty was the first full leg amputee to summit Mount McKinley without an artificial limb in 1985. Ed Hommer was the first double leg amputee to reach the top of Denali in 1999.
If the soldiers are fortunate enough to summit, some have celebratory moments planned.
Martin, an Arizona Highway Patrolman, wants two pictures taken at the top of Mount McKinley. One is of the team, and the other will be of him displaying a patch from the Arizona Department of Public Safety.
"I want to show them that I do appreciate (them) sticking with me, not just saying, 'Hey, we're really sorry it happened to you, good luck in the future,'" he said. "But not only that, but had faith in me that I can do the job."
The expedition's only active duty military member, Marine Capt. David Borden of Hanover, Pa., had his right leg amputated above the knee after an attack by a suicide bomber in Iraq in 2008.
"Obviously I was injured, but my family and friends were also injured. Making the top is for them as well," Borden said, "and my way of thanking them for everything they did for me and the support they gave me."