He didn’t talk much, at home, about what he did “in theatre.” On one tour, his unit was assigned to guard the United States Embassy, a task that included searching Baghdad, both on foot and in mechanized patrols, for insurgents launching attacks on the Green Zone. On another tour, in 2005-06, his unit spent seven months fighting in Saqlawiyah, northwest of Falluja, in Anbar Province. Mike Tucker, an embedded writer and former marine who went on patrol with Twiggs, wrote, in “Ronin,” a book published last January, that Twiggs was “regarded in the U.S. military as one of the best combat trackers alive.” His men adored him, Tucker said.

Travis never doubted the wisdom of the war, Kellee said, and he was frustrated by the press coverage it got. “He could see how it was helping people. But all they showed were the bad things. His thing was, everybody flew flags after 9/11 for seven, eight months. Then it got ‘old.’ He was pissed about that. Americans didn’t appreciate the military. Then, after his third tour, we’d be watching the news and there would be some horrible American shit going on—some adoption-fraud scam, or some people who threw a baby into a lake in a garbage bag. And Tebeaux would just start crying and shouting, ‘What the fuck am I fighting for?’ ”

Kellee said, “Nobody even noticed it in Two-Six”—Travis’s battalion—“but I did. He got so twitchy, it became impossible to cuddle with him. He loved movies, but he couldn’t sit still to watch one. You could just see the wheels turning. You wanted to keep him busy, keep him talking about things so he wouldn’t start talking about other things. He’d get upset when people asked him stupid things, like did he kill anybody, and he wouldn’t talk, but other times he’d start talking about I.E.D.s, and how horrible they were, how they put soap in them, so it sticks to you, and how they can detonate them with anything—a cell phone, a walkie-talkie. He’d hear a car coming up our gravel road here and he’d just hit the floor, just bam, because the tires crunching sounded like machine-gun fire to him. Or he’d just go sit upstairs and watch for lights—watch for Iraqis, because that’s what he used to do in Iraq. I’d call his name, get him back to bed, and the only way I could get him to sleep was to put him in a bear hug and rock him. Then he’d sleep. But as soon as I moved he’d wake up.”

Travis started drinking heavily, and having trouble concentrating. “His therapy was to cut the grass, with his iPod on,” Kellee told me. “He did that a lot.”

It was dark now, with a full moon rising. Kellee hadn’t touched her food. “He volunteered,” she said. “We volunteered. He did what he did because he was fucking awesome, and he kicked ass because he loved his country. And when he got sick, got saddened, his government, his Marine Corps, let him down.”

She started to cry. “He was so beautiful,” she said.

It has been called by different names—shell shock, battle fatigue—in different eras, but P.T.S.D., in its combat form, has been around for as long as war has. Odysseus and his men had it. Although Twiggs used the word “paranoid” to describe his mood when he was Stateside, the more accurate term, used by P.T.S.D. researchers, might be “hypervigilance”—a normal adaptive strategy for surviving combat, except that the “on” switch is not easily turned off. Dr. Jonathan Shay, a P.T.S.D. specialist, thinks that even calling it a disorder is misleading: P.T.S.D. is an injury. There are degrees of damage, ranging from standard combat stress, which can be treated with a few days’ rest, to full-blown complex P.T.S.D., which is very difficult to treat, let alone cure. It is best understood, though, as a psychic wound, one that can be crippling, even fatal, in its myriad complications.

Compared with other American wars, the conflicts in Iraq and Afghanistan seem to be producing victims at a high rate. A recent RAND Corporation study estimated that three hundred thousand veterans of America’s post-9/11 wars—nearly twenty per cent of those who have served—are suffering from P.T.S.D. or major depression, and many more cases are expected to surface in the years ahead. This elevated rate is generally attributed to the rigors of a long war being fought without conscription: multiple deployments and heavy use of National Guard and reserve units. And on the ground, at unit level, the discouragement of anyone with stress symptoms from asking for help is intense. The same RAND study found that, mainly because of the stigma still attached to P.T.S.D., only half of those afflicted have sought treatment.

The suicide rate among veterans and active-duty military personnel has been rising as well. The number of soldiers who killed themselves last year was the highest since the Army began keeping records, in 1980. When Dr. Ira Katz, the Department of Veterans Affairs chief of mental services, learned earlier this year that preliminary internal reports suggested that a thousand veterans in V.A. care were attempting suicide each month, he sent a colleague an e-mail saying, “Shh! . . . Is this something we should (carefully) address ourselves in some sort of release before somebody stumbles on it?” Another e-mail, written in March, 2008, by Dr. Norma J. Perez, a P.T.S.D. program coördinator in Texas, said, “Given that we are having more and more compensation seeking veterans, I’d like to suggest that you refrain from giving a diagnosis of PTSD straight out.”

Robert Gates, the Secretary of Defense, is said to be considering making some P.T.S.D. sufferers eligible for the Purple Heart. Wounded veterans are symbolically popular figures, if individually painful, and sometimes frightening. Certainly, most politicians want to be associated with their cause. And yet the difficulty of maintaining the troop levels necessary for the wars in Iraq and Afghanistan has placed the Bush Administration at odds with veterans’ groups. All such organizations supported what became known as the New G.I. Bill, which would provide increased education benefits. The Administration opposed it, on the ground that the appeal of a college education might sap troop levels. John McCain, himself a veteran, agreed. Ultimately, at the end of June, President Bush signed a modified version of the bill.

In the Marine Corps, the Wounded Warrior Regiment, created in 2007, marks a step toward the assumption of longer-term institutional responsibility for casualties, both physical and mental. “Used to be, we met them at the hospital door, shook their hand, thanked them for their service, gave them a discharge, and said goodbye,” Colonel Greg Boyle, the regiment’s commander, told me. “Now it’s marine for life.” Boyle did not mean that there would always be a place, a job, for disabled marines but that his regiment would track them and offer support throughout their post-discharge lives. P.T.S.D. victims are among those for whom the regiment is designed. It was Boyle who decided to send Travis Twiggs to the White House. “Nice guy. I liked him,” Boyle said.

Travis Twiggs didn’t announce his P.T.S.D. at first. When he returned from Iraq in 2006, after his third tour there, he was transferred to the Marine Corps Warfighting Laboratory, at Quantico. His superiors believed that his extensive field experience would be useful in the evaluation of new weapons systems and equipment. But without his beloved combat platoon, Kellee said, Travis was bereft: “He felt like he wasn’t in the Marines anymore.” And, at his office job in Virginia, his P.T.S.D. quickly became impossible to ignore.

His sergeant major recognized the symptoms, and, in June, sent him to a physician’s assistant, who prescribed the antidepressants Zoloft and trazodone. Antidepressants and antipsychotics are the main drugs used to control P.T.S.D. But, while his medications were being evaluated and adjusted, Twiggs was, by his own account, blunting their effect by mixing them with alcohol. He told Kellee that he couldn’t stand to look in a mirror. He was racked with guilt, in particular over the deaths of two young lance corporals in his platoon. The only thing that really helped, he wrote, was returning to Iraq. He went, in late 2006, on a weapons-testing mission for the Warfighting Lab, and, once again, his symptoms vanished. He wasn’t fighting, but at least he was in theatre. He was also good at his job.

But once he was home, in January, 2007, “he went batshit,” Kellee said. His P.T.S.D.—anger, sadness, drinking, flashbacks—took a toll on their marriage. She went to counselling for P.T.S.D. spouses—sessions led by Travis’s therapist. “I didn’t really see the point,” she says now. “I mean, a twenty-two-year-old girl gets up and says, ‘He’s got guns all over the house, including a 9-mm. he puts between the mattress and the box spring. And one night I woke up and he had the gun up to my head, calling me an Iraqi. So I had to talk him all through that, and get him to put the gun down.’ How long do you think that marriage will last?”

Travis soon landed in a locked ward at Bethesda Naval Hospital. “At Bethesda I was not exactly a model patient,” he wrote in his article. “I was experiencing psychosis where I would fight my way through the hallways and clear rooms as if I were back in theater. The hospital police would have to be called in to secure me.” He was later transferred to a veterans’ hospital in West Virginia, where he saw several doctors, “and it seemed that each one had a different medicine. I often wondered if they ever talked with each other.” At one point, he wrote, he was taking twelve different medications a day—Kellee recalls the number reaching nineteen, and says that the drugs turned her husband into “a zombie”—“and I was experiencing visual and audible hallucinations that I firmly believe were a direct result of being overmedicated. On any given day I was sad, mad, or depressed. I often felt that I was weak and not worthy of calling myself a Marine anymore. I slept covered in sweat every night and constantly shook uncontrollably. I got to the point where I believed PTSD was nothing more than an acronym created for weak Marines.”

This was raw, vivid stuff for the Marine Corps Gazette. Twiggs went on to describe his recovery, through therapy and reduced medication, and wrote, “I am back doing what I do best and what brings me the most enjoyment—training Marines and sailors.” He offered bullet-point advice to policymakers and P.T.S.D. sufferers, and included his e-mail address in case anyone in trouble wanted to contact him. But the article was primarily confessional: “My only regrets are how I let my command down after they had put so much trust in me and how I let my family down by pushing them away.” His P.T.S.D. was “not completely gone,” he wrote, but “life with my family is wonderful again.”

Twiggs was sought after as a motivational speaker, and he became the Wounded Warrior Regiment’s P.T.S.D. poster child. His symptoms, however, returned. He became impossible to live with. He was sent back to Bethesda Naval Hospital and was once again, Kellee thinks, overmedicated.

The experience that continued to cut Travis Twiggs most deeply was the loss of Jared Kremm and Robert Eckfield, Jr., the young lance corporals in his platoon. They were killed at Saqlawiyah, on October 27, 2005. Golf Company’s firebase was an old Baath Party hotel near a main supply route to Jordan and Syria. The hotel compound was taking daily rocket and mortar attacks from Al Qaeda in Iraq and from the Black Flags Brigades, a Sunni insurgent group. Twiggs was leading foot patrols through villages and along the banks of the Euphrates, searching for insurgents and for weapons caches. He was in his element. But some of the facilities at the hotel were poorly secured. There was no running water, and portable toilets had been set out in tents in the compound. These outhouses were vulnerable; Twiggs later told Kellee that he thought that the toilets should not have been outside at all, but in some downwind corner of the sprawling hotel—the stench would be worth the increased security. But he was not the commanding officer on the base. Still, experienced noncommissioned officers regularly let their superiors know what they should be doing. His unit had been at Saqlawiyah for only a month when Kremm and Eckfield took a direct mortar hit in the rest-room tents.

Twiggs was one of the first on the scene. Kremm had been hit in the face; Twiggs watched him die. Eckfield was alive but had severe head wounds. Eckfield was transported to a hospital near Falluja, and died that night. Kremm was twenty-five. He was from Hauppauge, Long Island, where he had been a high-school football star. Eckfield was twenty-three, and from Ohio. Twiggs had trained them both at Camp Lejeune, where they had been regulars at his and Kellee’s house. The Defense Department announced that they had died “from an indirect fire explosion,” and gave their families uninformative explanations.

Christopher Lowman, who was one of Twiggs’s closest friends, and who was also a staff sergeant in Two-Six—he is now a gunnery sergeant, and back in Iraq—told me, “When you train these boys, you tell them every day, ‘You do what I tell you, exactly what I tell you, and I will get you home.’ ” Mike Tucker talked to Twiggs the night that Kremm and Eckfield died, and later wrote, in an e-mail, “Something broke in Travis. . . . That night, he told me, ‘I feel responsible for their deaths.’ ” On a tribute Web site, FallenHeroesMemorial.com, Twiggs wrote, “I wish that I could erase that horrible day from my memory . . . but I can’t.”

Travis’s family, most of whom live in and around New Orleans, remained largely unaware of his struggles. His brother Will was an exception. Will came to Bethesda and spent a week at Travis’s bedside in March. In a journal that he kept on Navy Lodge stationery, Will wrote, “My loyalty has unequivocally been to Tebeaux. I hope God doesn’t take him away from me too.”

“Will thought of Tebeaux as a hero,” Kellee said. “And it really bothered him when he realized how bad he was hurting.”

“Everybody was crazy about Will except Will,” Nancy Twiggs said. She is Will and Travis’s stepmother. She and Douglas reared them both, for the most part, in Ama, Louisiana, twenty miles upriver from New Orleans. They still live there, in a one-story brick house with a big yard backing onto a patch of woods. Nancy put on a video of Will, eleven years old and flaxen-haired, competing in a citywide spelling bee. He gets “aphasia” right, then wins it with “ineluctable.” Travis, age nine, rushes onto the stage and hugs his brother. After the video ended, we sat in silence for a minute while Douglas and Nancy composed themselves.

“It’s like they’re still here,” Nancy said.

“We thought Will might be a sportswriter,” Douglas said.

Nancy and Douglas Twiggs are hospitable, heartbroken people. Will, they say, was a devoted, protective older brother. He and Travis were especially close. Each could mimic the other’s voice, and, even as adults, they liked to trick people over the phone, pretending to be the other. Will was disappointed, they thought, when Travis, in high school, suddenly decided to go live with their mother, in Miami. It was the first big decision he had made without consulting Will.

Will joined the Navy out of high school. In a snapshot taken aboard a ship in San Francisco, he looks, in Navy whites, very young and frail, like a bird that has left the nest too soon. The physical contrast with Travis, who was six inches shorter but many pounds of muscle heavier, is stark. Will did not last long in the Navy. He went to work for a German-owned ship-chartering company in New Orleans, where Douglas, too, worked at the time. Will did logistics, and seemed to do well, but he turned down the company’s offer to send him to Hamburg for advanced training. “He didn’t want to leave New Orleans,” Douglas said. “Both of his friends lived here.” He smiled faintly at the old joke.