Major General Hugo Salazar, adjutant general of the Arizona National Guard, told members of a U.S. House subcommittee on border and maritime security last month that the plans for the troops to leave the posts along the border where they have assisted Border Patrol as part of Operation Phalanx are progressing. Salazar said all National Guard operations associated with Operation Phalanx are slated to end in June.

"Throughout the duration of Operation Phalanx, the Arizona National Guard has supported the Department of Homeland Security in a commendable manner and the working relationship between National Guard and Law Enforcement has been nothing short of exemplary," Salazar told the subcommittee. "To complete all administrative and logistical actions required, operations will effectively stop no later than the second week of June."

Of the 560 guardsmen sent to Arizona, 504 are "dedicated to Border Patrol activity," said Border Patrol spokesman David Jimarez. That activity mainly involves surveillance, Jimarez said.

"[The guardsmen] have been acting in a sup­­port capacity," Jimarez said. "They act as our eyes and ears."

The guardsmen, although armed, don't have "any law enforcement responsibilities," Jimarez said. He added that the presence of the guardsmen, who are often highly visible while manning Skywatch towers near the border, adds an "increased deterrence factor" to would-be illegal border crossers.

The National Guard troops in Arizona are some of the 1,200 total troops deployed to the Southwest border last year.

In March, Customs and Border Protection Commissioner Alan Bersin told reporters that Arizona is the "centerpiece of the effort to bring the border under control."

"The men and women of Customs and Border Protection are here in numbers greater than ever before," Bersin said. "We have just over 6,000 CBP agents and officers... and (in the Tucson sector) the greatest concentration of aviation resources of any sector."

In August, President Barack Obama approved $253,900,000 in emergency supplemental funding to the Department of Homeland Security to add 1,000 new Border Patrol agents, 250 CBP officers, two more unmanned aircraft and two new forward operating bases along the Southwest Border.

Customs and Border Protection reported in January that National Guard troops along the Southwest border have assisted with the seizure of more than 14,000 pounds of illegal drugs since their deployment last summer.

Salazar said funding for Operation Phalanx coming from the Department of Defense totaled about $110 million – $34 million of which went to Arizona. That breaks down to approximately $60,000 being spent for each of the 560 guardsmen for the duration of their nine-month deployment.

Jimarez said the guardsmen have been "very effective" in deterring illegal entries and identifying and reporting intrusions to Border Patrol agents and that Border Patrol considers the collaboration a success.

But not everyone is thrilled about the withdrawal. Arizona Gov. Jan Brewer told The Arizona Republic pulling National Guard troops of the border is a mistake.

"It's inexcusable and inexplicable to consider withdrawal of National Guard troops from our southern border at a time when cartel violence continues and the security of the border region remains under threat from drug and human smugglers," she told The Republic. "Unfortunately, this appears to be further evidence that the White House is not fully committed to devoting the manpower and resources necessary to secure the border. Rather than withdrawing National Guard troops, the president ought to consider using them as a long-term tool to augment the nation's border-security strategy."