YUMA, Ariz. -- Over the past year, this sandy stretch of desert in southwestern Arizona has become the nation's busiest immigrant-smuggling hot spot, a place of increasing banditry, violence, desperation, and death.
Border Patrol agents are seeing increases in arrests of illegal immigrants and cases every day of criminals preying on border crossers.
President Bush will get an up-close look today when he visits Yuma as part of his push to overhaul the nation's immigration laws and tighten the 2,000-mile US-Mexico border by sending up to 6,000 National Guardsmen in a backup role.
An eastern Arizona stretch that includes Douglas and Nogales used to be the busiest spot along the border for immigrants trying to slip across. But authorities say a buildup there of border agents and surveillance technology caused a shift last year, pushing immigrants toward the Yuma Border Patrol station.
The shift is a common pattern seen in recent years: Crackdowns in one section of the border send immigrants and smugglers flooding to other areas, creating an ever-changing front.
''Yuma is becoming the focal point," said Richard Hays, Border Patrol spokesman.
At the Yuma station, which oversees 62 miles of the border, authorities said agents are catching 300 to 450 immigrants a day, which is comparable to last year's numbers, but they are seeing unusual spikes, including 840 on a single day in March.
Law enforcement authorities said the number of those who slip through is greater than the number caught, but they would not give any figures.
Along the entire 125-mile Yuma sector, of which the Yuma station is a part, Border Patrol agents have made 95,000 arrests since Oct. 1, a 13 percent increase from this time last year, authorities said. The number of Border Patrol agents assigned to the sector has doubled to about 700 in the past year.
An increasing number of immigrants who bypass fortified stretches of border are dying in the desert. Deaths in the Yuma sector hit a record 51 in 2005, up from 36 in 2004 and 15 in 2003.
Daytime temperatures in Yuma can climb to about 120 degrees -- 10 to 15 degrees hotter than around Tucson, in the state's eastern sector. Another danger: The area includes an Air Force bombing range.
The Yuma station relies largely on patrolling agents, radar, sensors, cameras, and observation towers. It has only a few miles of fences.
Thirty minutes south of Yuma, in one of the more active parts of the region, there are two lines of defense: a 12-foot corrugated metal fence that divides the city of San Luis from Mexico, and, about 50 yards north of the border, an 8-foot chain-link fence topped with barbed wire and towers with surveillance cameras.
Stadium lights help agents spot those who try to slip across under cover of darkness.
In the US community of San Luis, a few hundred yards from the fences, farm worker Salvador Martinez said immigrants try to open his back door or car at night in hope of finding a hiding place. He said immigrants running past his stucco house trample the roses and cactuses in his yard, where a ''Beware of Dog" sign is posted.
''They don't respect anything," Martinez said, taking a break from pulling weeds.
Many homeowners in San Luis have wrought-iron fences around their houses, and yet they cannot leave their garage doors open, for fear of thefts.
Roving gangs of bandits also wait in the dense scrub of the dry Colorado River bed for the right moment to hold up immigrants on their way to work in the United States.
''If you live here and your bicycle gets stolen, we might not be there for an hour or so because we have to respond to one of these robberies," said Captain Eben Bratcher, spokesman for the Yuma County Sheriff's Department.
Illegal immigrants also face threats from the smugglers who brought them across. Smugglers assault and extort money from their customers and are more likely these days to flee from police who try to pull them over, authorities said.
Some Border Patrol vehicles in San Luis have metal cages over their windows because of an increase in rock-throwing by smugglers who lash out at agents when stepped-up patrols make it harder for them to get across, according to authorities.
A quarter of work for the Yuma County Sheriff's Office is related to immigrant and drug smuggling. The office said that it spends nearly $2 million a year jailing illegal immigrants suspected of committing crimes north of the border and that only a fraction is reimbursed by Washington.
Yuma County Regional Medical Center estimates it has $2 million a year in unreimbursed costs for treating illegal immigrants.
Charles M. Davis III, who has lived in Yuma for 25 years, said ''draconian" steps are needed to stop the flow of immigrants and drugs across the border. ''Putting the military on the border is the only way I see to really stop it," Davis said.
Still, Davis said Bush's plan could be a drain on taxpayers.
''People are still willing to defy the risk of death," said Jennifer Allen, director of the Border Action Network, an immigrant rights group.