Very sadly, this is not a new story in America, but it’s once again, a tragically sad news story.

Ever since our nation first began sending its heroic young men — and now, its heroic young women — off to war, we have all watched as a segment of them come home and lose the terrible battles they now fight with their own horrific war memories, their own terrible physical and mental scars, and who very tragically and far too often wind up as yet another homeless veteran statistic.

The Civil War produced thousands of wandering homeless veterans. Many of them were addicted to morphine, and they quickly became known as ‘tramps,’ searching for jobs that weren’t there, and, in many cases, literally tending their own wounds.

More than a decade after the end of World War I, the ‘Bonus Army’ descended on Washington, D.C.  — demanding immediate payment for benefits that had been promised to them — and they were callously routed by the U.S. military.

And, perhaps most painfully, there was Vietnam: Tens of thousands of our war-weary veterans, quickly rejected, or forgotten, or despised, by their own government, and by so many of their own fellow citizens.

And now, unbelievably, it is happening again, in ever growing numbers, to a new generation of our veterans.

About 1,500 veterans from the wars in Iraq and Afghanistan have already been identified as being homeless. And only about 400 of them have been helped by programs designed to target homelessness.

These 1,500 vets are now very sadly part of an ever growing 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.

But as the war in Afghanistan now plods on into its seventh long year, and the war in Iraq into its fifth never ending year, a new cadre of homeless American veterans is quickly forming.

And with it come the same old questions: How is it that a nation that became so familiar with the homeless Vietnam veteran, is now again standing by, doing nothing, and simply watching, as more and more homeless veterans turn up from our new wars?

What lessons as a nation have we not learned? Who is failing our veterans? Is homelessness an unavoidable byproduct of all war, of all young men and women, who so selflessly devote themselves to serving their country, and who then see and experience things that no man or woman ever should?

Advocates for homeless veterans are now using words like ‘surge’ and ‘onslaught’ and ‘tsunami’ to describe what could very tragically happen in the coming years, as the wars in both Iraq and Afghanistan continue on and on, and thousands upon thousands of new veterans now find themselves struggling with post-traumatic stress, with horrific war injuries, and with homelessness.

Those who have studied postwar trauma say there’s a gap between coming home — the time of parades and backslaps and ‘The Boys Are Back in Town’ on the local radio and TV stations — and the moments of utter darkness that leave far too many of our veterans so very depressed, and far too often, homeless.

In that time period, some veterans focus on the horrors they saw on the battlefield, or on the friends they lost there, or why they themselves deserved to come home at all. They self-medicate, develop addictions, spiral downward, lose their families and friends, contemplate suicide, and eventually, become homeless.

How — or perhaps the better question is why — is this happening again?

Some veteran advocates say there are some factors unique to the Iraq war, like multiple deployments in the war zone, and the proliferation of improvised explosive devices (IEDs) 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 war front, Iraq and Afghanistan veterans have shown the signs much earlier.

This could also be because stress disorders are better understood now than they were a generation ago, advocates say.

"There's something about going back a third and a fourth time, that really aggravates that level of stress," said Michael Blecker, executive director of Swords to Plowshares," a San Francisco homeless-vet outreach program.

"And being in a situation where you have these IEDs, everywhere over there is a combat zone. There's really no safe zone there. I think that all is just a stew for post-traumatic stress disorder."

Others point to something more difficult to define - some terrible flaw in our American society and culture, in our government leaders, and in all of us, that — while celebrating and honoring our troops upon their homecoming — we then ultimately and tragically, very quickly forget them.

And that truly is a damned shame – for our nation, for our leaders, and for each and every one of us.