President Trump spread the idea on Tuesday to send troops to the US-Mexican border.
"Until we can have a wall and adequate security, we will guard our border with our military," said Trump White House.
He continued, "This is a big step, we have not really done that before, or at least not much sooner."
That's not true. The long-standing concern over the security of the southern border, quoted by Trump, led to the deployment of thousands of National Guard troops under President Barack Obama and George W. Bush.
It was not immediately clear why soldiers would be needed: the number of people illegally entering the country has dropped dramatically in the last decade and is at its lowest level since 1
Operation Jump Start, President Bush, 2006-2008
At the height of the war in Iraq and months before troop reinforcements took place there, Bush federated 6000 National Guard troops in California, Arizona, New Mexico and Texas. Another battle over the Mexico border seethed when Mexican officials declared war on drug cartels in late 2006, causing waves of killings and instability that spilled over.
Despite the presence of armed US soldiers and airmen, their mission was mostly passive, said Customs and Border Patrol. Laws known as "Posse Comitatus" prohibit the use of the military for national prosecution outside military bases. The troops focus on monitoring ground stations and helicopters and installing fences and vehicle barriers.
An Arizona National Guard watches over the US border with Mexico on December 7, 2010 in Nogales, Arizona (John Moore / Getty Images)
The troops were usually expected to be suspected drug traffickers and undocumented migrants / Do not capture and instead report activities to federal agents Troops on the frontier impacted what military personnel could do.
Under Title 10, for example, guards are under the command of the Secretary of Defense using federal funds. Troops activated under Title 32 are federally funded but under the command of the governor, where they are more flexible in law enforcement.
Officials said at the time that it was a necessary extension that allowed the agents to move for administrative and strategic reasons, infrastructure tasks and focus on ground operations.
But the $ 1.2 billion price tag raised questions about deploying troops to fulfill a Homeland Security Department mission when National Guard troops were depleted of rotations in Iraq and Afghanistan.
There were tensions at the border after a fatal incident in 1997 with the military? A US Navy shot and killed an American high school student who wore a .22 rifle that was mistaken for an enemy person while guarding goats on the Texas border, resulting in a temporary halt to military activity.
Operation Phalanx, President Obama, 2010-2016
The successor to Jump Start began with an Obama empowerment to deploy 1,200 troops along the border, again fearing that violence would ensue after some prominent killings north of the border Nick Miroff from the Post Office reported 2011.
Another reason: Customs and border guards It took time to fill their ranks with staff shortages.
National Guard troops later dispatched a fleet of UH-72 Lakota helicopters with infrared camera arrays to detect the movement of t he sky at night and through some of the leaves that migrants use as veiling.
A release from the guard said the helicopters normally contained a Border Patrol agent on board. The Lakotas used powerful radios that helped the agents communicate with each other and distributed units of the guard across large areas.
The Guard spoke of the deployments so that the soldiers could gain hands-on experience in the mission, which cost $ 110 million in 2010
. But the Government Accountability Office published a 2011 report outlining the Pentagon's concerns about the lack of strategy For troops deployed in a permanent DHS mission On their orders, the DHS left to find out how best to exploit them.
There were other concerns of the government.
"Department of State and Department of Defense officials raised concerns over Mexico's militarization of the US border, particularly when US Department of Justice officials are helping Mexico's civilian law enforcement agencies tackle crime and border issues." says the report. 19659026] The Federal Aviation Administration also said it feared that unmanned drones would be able to detect and avoid other aircraft near the border.
At the end of 2011, Obama shortened its mission to focus on air surveillance During this period, noteworthy implementations were made. In 2014 then-Gov. Rick Perry (R) sent about 1,000 Texas National Guard soldiers to the southern border after an influx of unaccompanied minors from Central America found asylum in the US. The Air Force bases were used as emergency shelters for the children.
Read more:  Jim Mattis said immigrants should not be deported. ICE tries it anyway.
Trump instructs military to begin planning for withdrawal from Syria
After a deceptive call with Trump over the border wall, Mexican presidents plan to visit the White House
A deported veteran has obtained US citizenship, after 14 Years in Mexico