Hundreds of thousands of homeless veterans will be walking into shelters and soup kitchens on Thanksgiving, and advocates warn that many more will follow if the United States does not prepare to assist soldiers returning from the current war in Iraq.

"We have to be almost hyper-vigilant when these guys get back," said Steve Robinson, executive director of the National Gulf War Resource Center (search), an advocacy organization for Persian Gulf War-era veterans.

U.S. veterans face a greater chance of becoming homeless than the general population, say experts. According to the National Coalition for Homeless Veterans (search), a study released in 1999 found that while veterans count for 9 percent of the entire population, they are nearly 23 percent of the homeless population and 33 percent of the adult male homeless population.

The 1999 report — the most recent of its kind — issued by the Interagency Council on Homelessness (search) showed that nearly 85 percent of homeless vets have high school or graduate equivalency degrees, as opposed to 56 percent of non-veteran homeless.

"There are many homeless veterans sleeping in the streets of America," said Linda Boone, executive director of the NCHV.

Boone said no "sound bite" causes or solutions can explain the circumstances that lead veterans to become homeless. But Robinson and other experts note that 76 percent of all homeless vets — about 500,000, according to estimates — have substantial substance abuse and mental health problems.

These experts contend that in many cases, problems stem from post-traumatic stress disorder (search) caused by their military service.

The ICH study showed that as of 1996, nearly 47 percent of homeless veterans served during the Vietnam War and 17 percent served after Vietnam. Robinson said some troops in Iraq have seen Vietnam War-level carnage, a certain cause of post-traumatic stress disorder.

"When the combat is particularly devastating — like it is now — when those people come back they will change and forever be changed," said Robinson, pointing to the daily guerilla attacks on U.S. servicemen and women in Iraq. Approximately 130,000 soldiers are currently serving in Iraq, and have experienced nearly 300 casualties since May 1, the declared end of major combat.

"It's going to take aggressive counseling and services" to ensure soldiers don't fall into a spiral of depression when they return, Robinson said, adding that depression can lead to the kind of self-destructive behavior that has led many vets to eventual homelessness.

Nancy Verespy, executive director of Veterans of the Vietnam War (search), said post-traumatic stress disorder does not always affect veterans right away, nor are veterans necessarily homeless right after discharge. Sometimes, it takes years for depression, anxiety, substance abuse and bad economic situations to take their toll, driving them into the streets, she said.

"PTSD is an insidious thing, it creeps into the mind," she said. "Hopefully these younger vets will recognize their need sooner. Hopefully they will get help."

According to Veterans Administration officials, the federal government operates 134 outreach health care facilities that assist about 40,000 homeless veterans across the country. They also provide special services for the homeless at regional hospitals, have acquired properties for homeless shelters and provide readjustment services at its 206 Vet Centers nationwide.  The agency expects to fund soon about 8,000 beds for the homeless at 34 VA sites.

"We’ve exponentially increased our capability to reach out into the community right now, and from that standpoint we've improved," said Al Taylor, VA program specialist. "There are never enough resources to get out there and do everything we'd like to do, but we feel like we are making progress."

Rick Weidman, director of government relations with Vietnam Veterans of America, said he thinks the VA has worked hard to build a network of programs for the homeless that hadn’t even existed before the 1980s, but the VA is still serving only about one-fifth of the estimated veteran homeless population.

He said the department needs to put more resources into the right places to deal with mental illness in the veteran population, including more money toward prevention.

"We are simply not prepared to deal with the mental problems, or even the physiological problems at a healthy rate," he said. "We could prevent a great number of veterans becoming homeless in the first place."

Not all homelessness among veterans can be blamed on traumatic military service or a failure by the Pentagon to provide essential readjustment training to discharged soldiers, say some experts. Some veterans had mental health or life skills problems before they went into the military. Some are victims of substance abuse or a bad economy. Others don't want to be found.

"Does it all lay at the feet of the military? Probably not," Boone said. But, she added, she has not found an adequate explanation how so many veterans can leave the service with so few life skills, little wherewithal to get jobs or the ability to integrate back into society.

She said both the Veterans Administration and the communities to which these veterans are returning have an obligation to help provide job assistance, education and mental health counseling, if necessary.

"The community in which a veteran lives has to say, 'What can I do?'" Boone said.

Verespy said her group has been leading a campaign to get homeless veterans transitional housing. Called the "United Veterans Beacon House," (search) the project has funded special housing for veterans who have completed drug or alcohol rehabilitation, counseling and other assistance programs in Texas, New York, Pennsylvania, Virginia, Ohio, Louisiana and Florida.

Verespy said she has helped at least two veterans from the first Persian Gulf War find such housing, and expects she will see more of these veterans, who are typically in their 30s, after they return from Iraq.

"We need to support them because they’ve supported us. Veterans should never want for everything — maybe that’s not realistic, but it’s hopeful," she said.