Law enforcement authorities fear that the planned relocation of thousands of Army soldiers in Texas could trigger a battle the military has not trained for – a turf war between violent criminal gangs.

Local police and FBI officials said they expect the transfer of between 10,000 and 20,000 troops to Fort Bliss near El Paso, Texas, to bring more members of the Folk Nation gang into contact with a criminal group that is already well-established in the area, Barrio Azteca.

“What we have started looking at is which military units are going to be moving to El Paso,” an FBI agent there, Andrea Simmons, said in an interview. “There is a potential for more gang activity, whether it be soldiers, or dependents and families of soldiers.”

Ms. Simmons said some gangs actually direct members to join the military to learn how to handle weapons. “The intelligence that we have thus far indicates that they may try to recruit young people who have clean records and encourage them to keep their record clean to get into the military. They would get great weapons training and other types of training and access to weapons and arms, and be able to use that knowledge,” she said. “They’re taking training that is great and very altruistic and turning around and using it for criminal activity.”

Ms. Simmons said Folk Nation, which was founded in Chicago and includes several branches using the name Gangster Disciples, has gained a foothold in the Army. “The Folk Nation has a presence with the military and/or their dependents,” she said.

One FBI official, Jeremy Francis, told an El Paso television station, KFOX, that law enforcement had identified at least 80 people with military connections who had committed gang-related crimes. He said about 800 have some allegiance to Folk Nation.

The executive director of the National Major Gangs Task Force, Edward Cohn, said those numbers do not come as a shock. “People are initially surprised that there are gangs in the military, but really it shouldn’t be a surprise,” he said. “For somebody to believe there are no gangs in the military would be very naive.”

Mr. Cohn also said some gang members refine their techniques in the Army. “There is a sophistication there,” he said.

An analyst of extremist groups for the Anti-Defamation League, Mark Pitcavage, said the military and the gangs both recruit from the same strata of society.

“A lot of the young people who tend to get into street gangs, they tend to come from socioeconomic backgrounds where joining the military is very economically desirable,” he said. The discovery of gang members in the military is “not uncommon at all,” he said.

Officials from the Army’s Criminal Investigation Division did not return calls seeking comment for this story. However, Army investigators have posted on the Web a PowerPoint presentation telling military commanders how to identify gang tattoos, graffiti, and paraphernalia.

“There is ample evidence that members of the Armed Forces had previous, or have current and active contact with criminal street gangs or extremist groups,” the presentation says. It describes incidents, some as far away as Europe, where military members or their children have been involved in gang-related violence.

Mr. Pitcavage said the armed forces generally do a good job of trying to keep out gang members. “If you’re in a street gang, the military doesn’t want you. Recruiters, they want to see all your tattoos,” he said. “Just by virtue of there being so many thousands of people entering the military every year, they can’t catch everybody.”

A member of the El Paso gang unit, Sergeant Mary Lou Carrillo, said some gang members join the military with the intent of making a clean break. “Some members truly want to change their life and get out of this situation. Then you have others who join with the purposes of continuing in the gang,” she said. “That’s our problem, unfortunately, a lot of people still having that loyalty to the gang.”

The current wave of concern was triggered by plans agreed on last year to move as many as 20,000 troops to West Texas from a variety of locations, including Fort Hood near Killeen, Texas. The base realignment process has always been fraught with political peril, but the suggestion that it could lead to gang violence seems to be a novel one.

Ms. Simmons said the influx could upset the “controlled chaos” created by the dominance of Barrio Azteca in El Paso. Like other gangs, it controls the drug trade, and engages in burglaries, robberies, and shootings.

“Could there be some serious turf wars?” Ms. Simmons asked. “We haven’t seen that in El Paso. Is that what may be coming?”