They return from the battlefield but are not exactly back home. If anything, they are thrown out as they are out of sync with their own family members. This phenomenon of homeless young veterans is beginning to assume disturbing proportions in the US.
Peter Mohan never did find a steady job after he left Iraq. He lost his wife, a judge granted their divorce this fall, she just could not stand his highly erratic behaviour.
He lost his friends and he lost his home, and now he is in a shelter for the homeless.
He is only 28 years old. "People come back from war different," he offers by way of a summary when asked about his personal problems.
Or take Mike Lally.
It was in 2004, when he came back from his second tour in Iraq with the Marine Corps, that his own bumpy ride down began.
He would wake up at night, sweating and screaming, and during the days he imagined people in the shadows — a state the professionals call hypervigilence and Mike Lally calls "being on high alert, all the time."
His father-in-law tossed him a job installing vinyl siding, but the stress overcame him, and Lally began to drink. A little rum in his morning coffee at first, and before he knew it he was drunk on the job, and then had no job at all.
And now Mike Lally, still only 26 years old, is homeless, booted out by his wife, padding around in an old T-shirt and sweats at a shelter called Soldier On.
These are not a new story in America: A young veteran back from war whose struggle to rejoin society has failed, at least for the moment, fighting demons and left homeless.
But it is happening to a new generation. As the war in Afghanistan plods on in its seventh year, and the war in Iraq in its fifth, a new cadre of homeless veterans is taking shape.
And with it come the questions: How is it that a nation that became so familiar with the archetypal homeless, combat-addled Vietnam veteran is now watching as more homeless veterans turn up from new wars?
What lessons have been learnt? Who is failing these people? Or is homelessness an unavoidable byproduct of war, of young men and women who devote themselves to serving their country and then see things no man or woman should?
For as long as the United States has sent its young men — and later its young women — off to war, it has watched as a segment of them come home and lose the battle with their own memories, their own scars, and wind up without homes.
The Civil War produced thousands of wandering veterans. Frequently addicted to morphine, they were known as "tramps," searching for jobs and, in many cases, literally still tending their wounds.
More than a decade after the end of World War I, the "Bonus Army" descended on Washington — demanding immediate payment on benefits that had been promised to them, but payable years later — and were routed by the U.S. military.
And, most publicly and perhaps most painfully, there was Vietnam: Tens of thousands of war-weary veterans, infamously rejected or forgotten by many of their own fellow citizens.
Now it is happening again, in small but growing numbers.
For now, about 1,500 veterans from Iraq and Afghanistan have been identified by the Department of Veterans Affairs. About 400 of them have taken part in VA programs designed to target homelessness.
The 1,500 are a small, young segment of an estimated 336,000 veterans in the United States who were homeless at some point in 2006, the most recent year for which statistics are available, according to the National Alliance to End Homelessness.
Still, advocates for homeless veterans use words like "surge" and "onslaught" and even "tsunami" to describe what could happen in the coming years, as both wars continue and thousands of veterans struggle with post-traumatic stress.
People who have studied postwar trauma say there is always a lengthy gap between coming home — the time of parades and backslaps and "The Boys Are Back in Town" on the local FM station — and the moments of utter darkness that leave some of them homeless.
In that time, usually a period of years, some veterans focus on the horrors they saw on the battlefield, or the friends they lost, or why on earth they themselves deserved to come home at all. They self-medicate, develop addictions, spiral down.
Mental illness, financial troubles and difficulty in finding affordable housing are generally accepted as the three primary causes of homelessness among veterans, and in the case of Iraq and Afghanistan, the first has raised particular concern.
Iraq veterans are less likely to have substance abuse problems but more likely to suffer mental illness, particularly post-traumatic stress, according to the Veterans Administration (VA). And that stress by itself can trigger substance abuse.
Some advocates say there are also some factors particular to the Iraq war, like multiple deployments and the proliferation of improvised explosive devices, that could be pulling an early trigger on stress disorders that can lead to homelessness.
While many Vietnam veterans began showing manifestations of stress disorders roughly 10 years after returning from the front, Iraq and Afghanistan veterans have shown the signs much earlier.
That could also be because stress disorders are much better understood now than they were a generation ago, advocates say.
"War changes people," says John Driscoll, vice president for operations and programs at the National Coalition for Homeless Veterans. "Your trust in people is strained. You've been separated from loved ones and friends. The camaraderie between troops is very extreme, and now you feel vulnerable."
The VA spends about $265 million annually on programs targeting homeless veterans. And as Iraq and Afghanistan veterans face problems, the VA will not simply "wait for 10 years until they show up," Pete Dougherty, the VA's director of homeless programs, said when the new figures were released.
"We're out there now trying to get everybody we can to get those kinds of services today, so we avoid this kind of problem in the future," he said.