McGuire said the mission, formally called "Operation Guardian Shield", will extend through September 30, 2018.
Last week, President Donald Trump ordered the Defense and Homeland Security departments to use National Guard troops in order to halt illegal border crossings and drug trafficking. Although New Mexico Gov. Susana Martinez has - as the Santa Fe New Mexican reports - "been critical in the past of the president's approach to border security and immigration", her office said this week the state is deploying 80 National Guard troops this week and expects to eventually deploy 250.
Trump has said that he wants as many as 4,000 guard members to assist Border Patrol agents until a wall is built. The Republican governors of Texas, Arizona and New Mexico on Monday committed 1,600 Guard members to the border, giving President Donald Trump numerous troops he requested to fight what he's called a crisis of migrant crossings and crime.
At that time, he added, the federal government will determine whether it has the budget and whether the mission is necessary to continue.
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He says none of the troops who are being deployed are required to carry guns but that they can do so if they feel the need to protect themselves.
Seen in the context of Trump's insistence on "sealing up our Southern Border", as he wrote on Twitter, Brown's announcement was hardly a vote of confidence.
Those are the groups of migrants, Brown told Mattis and Nielsen, that he does not want Guard troops in California taking into custody. It will not be a mission to round up women and children or detain people escaping violence and seeking a better life. Customs and Border Protection report, there was a 37-percent increase overall in March, when compared to February and a 203 percent increase compared to March of previous year.
Maj. Gen. Michael McGuire, the adjutant general for the Arizona National Guard, said 60 National Guard troops will be in place in Nogales on Friday.
"Here are the facts: there is no massive wave of migrants pouring into California", the governor wrote.
The state's guardsmen provided "targeted assistance" in 2006 under then-President George W. Bush and in 2010 under President Obama.