In the United States, Native Americans are the ethnic group with the highest proportion of people joining the military. They make up only about one percent of the population, but 1.6% of the armed forces. They are also more likely to suffer from post-traumatic stress disorder.
Life on the reservations is blighted by very high levels of unemployment, alcohol abuse, domestic and other violence, etc. The military offers a way out, a chance to pay for education, and a job.
But there are also cultural reasons, which, if anything, are even stronger: the warrior tradition, the high respect in which veterans are held in Native communities, and a patriotism that arises from a traditional belief in the need to defend Mother Earth.
But when American Indians go to war, their cultural heritage means they are more likely to suffer post-traumatic stress. In Vietnam, for example, the rate was about double that of white soldiers.
In this week's Crossing Continents, Robert Hodierne travels to the American South-West to find out why Native Americans enrol and suffer in such great numbers.
He also goes to see how therapy centres are now using traditional ceremonies to help sufferers.
Some people think that Native American soldiers suffer greater post-traumatic stress because they identify with their enemies in a way others do not, not least because of their own history of oppression. These reasons are culture-specific, and now the treatment is, too.
In the Southwest, the federal government has contracted medicine men, to offer treatments like sweat lodge sessions, drumming, and spiritual and herbal practices. Can these work where mainstream counselling has failed? And if so will they be rolled out to clinics across the country?
BBC Radio 4's Crossing Continents will be broadcast on Thursday, 20 December 2007 at 1102 GMT. It will be repeated on Monday, 24 December 2007 at 2030 GMT
Reporter: Robert Hodierne
Producer: Arlene Gregorius