There are from 200,000 to 300,000 homeless vets in the United States, 10 percent from 1991 Gulf War or the current one, 40 percent from Vietnam. Veterans are overrepresented in the homeless population. (Forty percent of homeless men are veterans, although veterans comprise only 34 percent of the general adult male population.) The AP report notes some are suffering residual stress that makes it tough for them to adjust to civilian life; some have a hard time navigating government-assistance programs; others just can't afford a place to live.
Contrary to what we might think, though, homelessness is not clearly related to combat experience--at least according to studies cited by the National Coalition for the Homeless. Research in fact shows that homeless veterans appear less likely to have served in combat than housed veterans; also, veterans at greatest risk of homelessness are those who served during the late Vietnam and post-Vietnam era; and homeless veterans are more likely to be white, better educated, and previously or currently married than homeless nonveterans.
For the most part, homeless veterans are prey to the same larger trends that afflict the general homeless population: lack of affordable housing, declining job opportunities, and stagnating wages.