AYESHA RASCOE, HOST:

The Biden administration is deploying 1,500 active duty military to the southern border this week. The White House says they won't be there to patrol the border, but instead will help with administrative work. Many more people are expected to try to enter the United States with the end, later this month, of pandemic-era restrictions. They allow the U.S. to refuse entry to more asylum seekers. It's the latest in a long history of posting U.S. troops at the southern border. To talk about that history, I'm joined now by Arizona State University professor of Latin American history, Alex Avina. Welcome to the program.

ALEX AVINA: Thank you so much for having me.

RASCOE: So let's start with your reaction. What did you think when you heard that troops were heading to the Mexican border once again?

AVINA: You know, I had a very typical historian response to this by thinking this is actually the rule when it comes to U.S.-Mexico border politics, not the exception. Because if we think about the history of the U.S.-Mexico border, it required the U.S. invasion of Mexico to create what is now known as the U.S.-Mexico border. So this is part of a long history, and Biden has joined with a series of his predecessors that goes back to the mid-19th century.

RASCOE: I mean, so his immediate predecessor, President Trump, deployed active duty troops to the border to help processing, you know, large caravans of migrants. The Biden administration says this is different from that, that troops won't be there to enforce the law or to intimidate migrants. I should say that, you know, the Trump administration also said that they weren't there to police, but the Biden administration says that the troops that they are sending there will free up Border Patrol officers to do on-the-ground work. What do you think about this distinction that the Biden administration is trying to make?

AVINA: I don't see much of a distinction at all. I mean, primarily there's a legal aspect to this that goes back to the late 19th century - right? - with the Posse Comitatus Act, which explicitly lays out that the U.S. Army cannot participate in domestic law enforcement capacities. So there really isn't that distinction legally or historically. I think it's a political distinction.

RASCOE: I mean, so you mentioned that this is a very long history. Can you talk to me about the history of American troops at the border, you know, recognizing that obviously the way that, you know, the U.S. got the southern border was through military action? But in more recent history, as you talk about the '70s, '80s, '90s, what is the history of American troops at the border?

AVINA: I think one way to understand, just, like, the U.S.-Mexico border from a U.S. military perspective is to think about it as a site of one of these forever wars. With the onset of particularly Mexican undocumented migration in the '70s and '80s, you started to see presidents, particularly like Ronald Reagan, start to conflate things like the war on drugs with undocumented migration into an issue of border security. And that's when you start to get increasing militarization of the U.S.-Mexico border. It creates a much more lethal space for people who are trying to cross into the United States.