An Army officer writes to libertarian Matt Welch on his Substack: Mailbucket #3: Immigration from the Inside, by Matt Welch, The Fifth Column (A Podcast), March 13, 2024.

Emphasis added:

 I just listened to peasant Episode #444 and was enticed by the friendly disagreement between Matt and M.M. on U.S. illegal migration numbers to possibly help shed some light. 

From December of 2019 through November of 2020 I was an active-duty Army officer assigned, alongside the rest of my brigade combat team, to augment CBP forces alongside the Texas, New Mexico, and Arizona border. Attached to us were an additional 400 National Guardsmen from various states. 

As active duty forces we were held under Title 10 authority, meaning we could not personally detain migrants or suspected migrants

I alway find this annoying. Obviously, the Posse Comitatus Act, meant to prevent the Army from being used on American citizes, doesn’t apply to guarding the border. Guarding national borders is what armies are for.

However, what we did was man two-person observation posts roughly each 1-2 miles across the entire southern border. My battalion was directly responsible for the area spanning from Laredo to Del Rio, Texas. Including Eagle Pass. 

Our job was to alleviate the [Observation Post] duty from the Border Patrol so they could more freely respond to sightings and interdict migrants crossing illegally. We were also there four months before, and then the rest of our time during, Title 42—essentially making us and the BP yell to migrants to turn around and go back to Mexico. 

CBP had three criteria we classified migrants into:

1) Turnbacks

2) Interdictions

3) Gotaways

During the 11 months we were there, we directly led to the interdiction of 34,500ish migrants. These included both ones that attempted to evade the BP and those that walked up to us and surrendered. After Title 42, we started tracking turnbacks, which were an estimated 75k, specifically in the corridor between Del Rio and Eagle Pass alone. 

Gotaways were harder to count. We evaluated gotaways as people we saw through either binoculars or FLIR cameras who were not successfully interdicted by the CBP.

Our estimation was roughly 110k or so, due to either migrant waves, which occupied CBP resources; weather, or the somewhat undulating terrain of parts of the border. 

This was before the repeal of Title 42. While this is chiefly anecdotal, and hard to either prove or disprove, the notion that the number of migrants that are interdicted are equal to the number that get away is laughable. 

In fact, according to ONE Army officer in this one battalion, guarding, if you can call it that, one heavily trafficked section of the border, the “gotaways“ are three times the number of the ones “interdicted“ by the Border Patrol. Something to think about when you see CBP figures on border crossings.