But anyone expecting to see a phalanx of U.S. soldiers standing guard along the 2,000-mile stretch with Mexico will be sorely disappointed. The troops aren't expected to be in place until early September and, when they are, will largely remain unseen in support roles.
"There is a misunderstanding about what deployment means," said Border Patrol Agent Mario Escalante of Arizona's Tucson sector. "It's starting to unfold; we've gotten several people in, we're starting to look at what we have and where we might need them [more troops]."
President Obama in May authorized the deployment, sending 524 troops to Arizona, 250 to Texas, 224 to California and 72 to New Mexico. More than 100 additional troops from the border states will serve in command and control positions. The troop roll out began Sunday.
Outside El Paso, Texas, which sits across from Ciudad Juarez -- one of the most dangerous cities in Mexico -- the Border Patrol has yet to receive assistance from the National Guard. Also unknown is if or when troops will arrive, Border Patrol spokesman Doug Mosier said.
"Having the extra troops helped us a lot in previous support operations we've done," said Mosier, who has spent 23 years with the Patrol and was involved with the Guard's deployment along the border during the George W. Bush administration. "But we don't have any yet, to my knowledge."
The troops are expected to assist border patrol agents and local law enforcement by providing intelligence and intelligence analysis, surveillance and reconnaissance support, and the ability to train additional Customs and Border Protection agents.
"The Aug. 1 date was when we could start training volunteers and handing out orders," Lt. Valentine Castillo of the Arizona National Guard said, noting that the deployment has been tied to the timing of federal funding for the move.
Castillo also said the Arizona Guard has yet to receive the 524 applications it needs for volunteers to make one-year, active-duty commitments, which would require them to temporarily leave their civilian jobs to assist Border Patrol.
"These are National Guardsmen and they only train one weekend a month so it takes some time to get them ready," he said.
Some GOP lawmakers, including Arizona Sens. John McCain and Jon Kyl and Arizona Gov. Jan Brewer, have criticized the size and urgency of the deployment as inadequate.
In the past few months, aggressive Mexican drug smugglers and migrants have harassed residents of Cochise County in Arizona's southeast corner, burglarizing homes and taking food and clothing, local law enforcement officials say.
The situation is part of what Brewer has characterized as "murder, terror and mayhem" and used as justification for the state's controversial new immigration law.
"It's simply not enough," McCain said in May. "We need 6,000."
McCain and Kyl Friday unveiled a 10-point "border plan" in which they called for more than $700 million in enhanced security measures, including 1,200 Border Patrol agents and 500 Customs and Border Protection officers.