DESPITE ITS PROXIMITY to Australia, New Guinea is geologically a much younger land. Shaped by the explosive tectonic forces of the Pacific Ring of Fire and carved by near constant rain into a tangle of swamps, trackless ravines, and 12,000-foot mountains, it is one of the most rugged and mysterious places on earth.

The world's second-largest island, New Guinea is divided between two countries. The western half, originally colonized by the Dutch, has been part of Indonesia since 1969 and is called Papua (the name was changed from Irian Jaya in 2002). Since gaining its independence from Australia in 1975, the eastern half, roughly the size of California, has been an independent nation called Papua New Guinea (PNG). Though tourism is still in its infancy, adventurous travelers visit PNG for wreck and reef diving, sea kayaking along its incredible coastline, and the chance to see birds found nowhere else in the world. For the ultra-adventurous, New Guinea offers challenging treks, mainly on the Kokoda, a 60-mile WWII trail, 40 miles northwest of the Kapa Kapa.

Still, vast swaths of the island remain unknown, and it's hard to imagine what WWII soldiers might have encountered here. In 1942, the Japanese landed 11,000 troops on the Papuan Peninsula's north coast, hoping to use New Guinea as a stepping stone to invade Australia, or at least to disrupt the supply lines from the United States to the South Pacific. MacArthur, who had been spirited out of the Philippines in March 1942 to command the Allied forces in the southwest Pacific and lead the Army effort against the Japanese, sent in Australian soldiers to stop them. Two months later, with the Japanese gaining a stronger foothold on the peninsula, MacArthur ordered a battalion of the American 32nd Division to cross the treacherous Owen Stanley Range and fight them at Buna. None of the men had spent a single day in the jungle.

Nor had I, but our team contained no slouches. I had logged hundreds of miles on foot and snowshoe through Arctic Alaska while researching my first book, and had been hiking with an 80-pound pack for eight months prior to this trip. Besides George, a 58-year-old long-distance runner and biker, our expedition group consisted of Dave Musgrave, 54, a wilderness expert and professor of oceanography at the University of Alaska–Fairbanks; Philipp Engelhorn, a fit 37-year-old Hong Kong–based photographer; Lee Ticehurst, a 55-year-old Aussie expat living in Port Moresby and an accomplished jungle trekker who has completed the Kokoda three times; a young three-man film crew (Cal Simeon, Jack Salatiel, and Kenneth "Samu" Pasiu) from Port Moresby–based POM Productions, there to shoot a documentary; and teams of porters hired in various villages along the way to carry our food and camping gear.

It took the WWII soldiers seven weeks to reach the north coast. They walked for more than half of those days; the rest of the time, they recuperated in villages and waited for food and supply drops. The Army's decision to let the men rest seemed practical at the time, but it backfired. The soldiers were already suffering from dysentery, trenchfoot, and jungle ulcers when malaria hit them like a bomb. Eventually, 70 percent of the division would contract the disease. We decided to walk considerably faster, even if it meant putting in 10- and 11-hour days on the trail. Concerned about malaria and battery power for the film equipment, our plan was to reach the end at Buna village in two to three weeks, limiting our exposure to the jungle.