Personnel and equipment prepare for departure from Fort Campbell, Ky., on Tuesday. (Maj. Martin Meiners/DVIDS/EPA-EFE/Shutterstock) (Maj Martin Meiners/Dvids Handout/EPA-EFE/REX/Shutterstock)

Troops have begun to deploy to the U.S. border with Mexico to meet a caravan of immigrants making its way north primarily by foot. As of Tuesday, the caravan was about 870 miles south of Brownsville, Tex., a 10-day walk -- walking 24 hours a day. American armed forces, traveling by plane, will probably arrive well before the caravan.


(Philip Bump/The Washington Post)

President Trump announced this week, with midterms looming, that the initial deployment would include a little more than 5,000 troops. In a conversation with reporters Wednesday evening, though, he floated a higher number: Maybe 10,000. Maybe even 15,000.

In the abstract, that seems like a fairly subtle distinction. If you’re going to send 5,000 troops to await however many of the estimated 4,000 members of the caravan make it to the border, why not just turn that dial up to 11? Trump pledged a “wall of people” barring entry to the United States. Figure that each person is about two feet wide, and 5,000 troops standing shoulder to-shoulder covers only a bit less than two miles. Put 15,000 people down there, and you’ve got a 5.7-mile human wall. Much more effective, at least as a wall.

But in the scale of deployment of forces internationally, 15,000 is a big commitment. There are only three countries where there are more than 15,000 active-duty U.S. troops deployed: Japan, Germany and South Korea. Data for Afghanistan, Iraq and Syria are no longer released biannually, but the most recent Defense Department data released suggests that there would be more troops at the border than serving on active duty in any of those countries.


(Philip Bump/The Washington Post)

Side note: The United States has a lot of troops positioned around the world.

If we count all members of the military, the number Trump has floated putting at the border is now surpassed by Afghanistan (at least as of 2017). Otherwise, it’s more members of the military than are deployed in any other country, including in Europe or the Middle East.


(Philip Bump/The Washington Post)

Notice on that map that the number of service members in Puerto Rico is much larger once you include non-active-duty personnel. Those individuals are mostly still working to aid with the recovery from Hurricane Maria.

If 15,000 troops were deployed to the border, there would be more people stationed there to fend off a few thousand migrants than are on Puerto Rico, aiding that island’s 3.3 million people.

In fact, deploying 15,000 troops to the border would constitute more service members than are on active duty in 64 different countries, according to the International Institute for Strategic Studies. In other words, if any of 64 specific countries threw their entire active military at our southern border, we’d have enough troops to fend them off.


(Philip Bump/The Washington Post)

It’s unlikely that Trump will approve that level of deployment. It will be interesting to see, in fact, how long the already assigned 5,000-plus troops remain in that region. Election Day is Tuesday, and a cynic might note that there’s a possibility that Trump is using the deployments to hype immigration as an issue before voting concludes.

It’s quite possible that the troops will have been deployed and rescinded before the caravan even arrives.

clarification: The duration of an 870-mile walk was clarified to explain that the distance could be covered in 10 days, according to Google, if walking without pause.