If National Guard troops were sent to the Arizona-Sonora border, it would be the third deployment in the last 11 years.
Roughly 1,200 National Guard troops were stationed along the length of the U.S.–Mexico border in 2010-11, including about 500 in Arizona.
The goal of Operation Phalanx, which cost $135 million, was to observe illegal border crossings and report them to Border Patrol. The operation shifted to aerial surveillance in late 2011.
About 6,000 National Guard troops were stationed on the border 2006-08 in Operation Jump Start, including about 2,400 in Arizona. Their goal also was to observe crossings and report to Border Patrol agents. The cost of the operation was $1.2 billion.
The operation was designed to support the Border Patrol while the border fence was expanded and several thousand Border Patrol agents were hired and trained.
The operation also allowed more agents to work in the field, rather than handle administrative tasks.
Since the 1990s, the Arizona National Guard has an ongoing role in fighting drug-trafficking through the Joint Counter Narco-Terrorism Task Force.