It's been tough to get the Texas out of Carter. His grandfather Walter Wilson Carter was such a good stalker that he'd sneak up on a deer and smack it on the rump. Carter's geologist father, Walter Jr., who taught him marksmanship and animal-tracking skills, would break up road trips across Texas to teach his son about fossils. By age six, Carter owned his first .22. By the time he was eight, he'd upgraded to a .222 rifle and a .410 shotgun. In high school, he'd wake up before dawn to check his raccoon-trap lines. And by the time Carter graduated from the University of Texas, in 1989, he had climbed every notable peak in the Rockies.

"John was a very easy child," says his mother, Emma Roy, a real estate agent in Nashville. "He could motivate people—that was his gift. And he feels very, very passionate about things."

After college, to Emma's horror, Carter joined the Army. At Airborne school, on his second jump, his right ankle cracked as he hit the ground. Carter left his boot on all night to reduce the swelling, ran five miles back to the airfield the next morning, then jumped out of the plane again.

His intensity eventually earned him a spot as the senior scout of an Airborne Ranger unit, the long-range surveillance detachment team assigned to the 101st Airborne Division, which pulled off dangerous missions in the Persian Gulf War from August 1990 to March 1991.

"Infantry quotes still rattle through my head on a daily basis," says Carter. " ‘You gotta live hard to be hard' and ‘Hard times don't last, but hard men do.' "

In 1991 in Iraq, Carter's six-man team was assigned a recon mission 93 miles into enemy territory. As the helicopter took off, Carter remembers, the pilot told the crew, "You are the craziest motherfuckers I've ever met."

Carter earned a Bronze Star for his efforts. "The military taught me how to be a warrior, how to fight, how to turn adversity into a weapon," he says.

After leaving the Army in 1992, Car­ter was accepted into Texas Christian University's Ranch Management Program, where he met a dark-haired beauty from Londrina, Brazil. Anna Francesca Carvalho Garcia Cid—Kika for short—was the granddaughter of Brazil's two most famous cattle breeders, Celso Garcia Cid and Rubens de Andrade Carvalho. In 1993 Carter asked Kika to marry him.

Beginning the day after the couple's honeymoon, Kika's father called Carter every Sunday for two years to try to convince him to take over his ranch in northern Mato Grosso. Carter finally caved and the couple moved to Fazenda Esperança in 1996.

Turns out, the Army was an ideal training ground for the Amazon. Carter has accidentally snorkeled into a nest of baby anacondas while clearing tree stumps in a swamp, survived a dog attack while hauling hunters in his Cessna (which ended with a bite on the back of his neck), and had an armed face-off with the chief of the Xavante tribe, who authorized his people to steal and kill 12 of Carter's cows. (Since then, Carter and the chief have become friends.)

"Psychologically, all this stuff scares the shit out of you, because ain't nobody going to pull you out," says Car­ter, comparing his Ranger days to life on the frontier. "But what's important is the mission. You may be terrified, but you still do it and complete it and it makes you feel stronger—almost invincible."

Carter's optimism scares his brother back in Texas. "He's a lighting rod. He's not from that culture and he never will be," says Will Carter, 52, who lives in San Antonio and runs his own oil-and-gas-exploration company. "You stand in front of a hot stove long enough and eventually you don't realize it's hot."

Shortly after Carter and Kika arrived at Fazenda Esperança, a cattle thief made off with their cows. Mad as hell, Carter grabbed his rifle and hopped on his four-wheeler. Kika jumped in front of Carter to stop him. He wouldn't budge. So Kika hopped on back.

"I remember thinking, How on earth am I going to send John's casket back to his mother?" Kika told me. "I thought, If he's going to die, I want to die, too. I don't want to deal with shipping his body home in a wood box."

By 2002, with a one-year-old daughter, Catarina, Kika had had enough of full-time frontier. The couple kept the ranch but moved to Goiânia, forcing Carter to get his fix of desperado life via Cessna commute.

The day after we arrive at Carter's ranch, we're scheduled to fly out after lunch, but he has to finish firing his tractor driver. Dave, Suzie, and I anxiously sit on the veranda and try to follow the heated conversation going on out back in Portuguese.

"What do you think of all this?" I ask Dave.

"I think it's the most original operation I've ever seen," he says.

"Would you ever sell a ranch in a place like this to an American?" I ask.

"The title's solid, and the potential for appreciation is strong," he says, looking around, "but it still has a few too many vestiges of lawlessness."