"We're going to do things militarily. Until we can have a wall and proper security, we're going to be guarding our border with the military," President Donald Trump said on Tuesday.
"We really haven't done that before, or certainly not very much before," he added.
About 24 hours after Trump said the U.S. hasn't often used the military to guard the border, Homeland Security Secretary Kirstjen Nielsen talked about such past military operations as inspiration.
"Today, what we've discussed are support activities that are very similar to Jump Start," Nielsen said.
"They include everything from aerial surveillance, which is as you know was part of Operation Phalanx," she added.
It turns out, every president since Ronald Reagan has authorized temporary military missions at the border. But those missions focused on surveillance and logistical support, not on arrests and use of force. That's because an 1878 law limits the military's power to conduct police action within the U.S.
President Obama's Operation Phalanx and President George W. Bush's Operation Jump Start are the two most recent deployments of the National Guard at the border. The missions helped with immigrant apprehensions and drug seizures. But they were also costly and happened at a time when illegal border crossings were more frequent.
In 2006, Bush sent 6,000 National Guard troops to California, Arizona, New Mexico and Texas to support border patrol agents while new recruits trained. The deployment lasted two years and cost $1.2 billion. A 2012 Government Accountability Office report says the troops assisted in arresting about 186,000 undocumented immigrants and helped seize some 316,000 pounds of marijuana.
When first announcing the deployment, Bush said in a national address: "The United States is not going to militarize the southern border. Mexico is our neighbor and our friend. We will continue to work cooperatively to improve security on both sides of the border."
In 2010, two years after the end of Jump Start, Obama launched Operation Phalanx — a similar, though smaller mission. The 1,200 troops that were deployed assisted in the apprehension of over 17,000 undocumented immigrants and the seizure of some 56,000 pounds of marijuana. After a year, Obama mostly halted the ground mission to focus on aerial surveillance. The first year of the operation cost $110 million.
"We do hope that the deployment begins immediately. ... It will be strong. It will be as many as needed to fill the gaps that we have today," Nielsen said.
During Wednesday's press briefing, Nielsen said the National Guard would be deployed to "assist the Border Patrol." She also said Trump is still working with governors to hash out a plan. She didn't have many details about how many troops would go, how long they would stay and, specifically, what they would do.
Later in the day, Trump signed a proclamation to confirm the move. And Mexico's government said Nielsen informed them that the deployed U.S. troops at the border wouldn't be armed.