Photos show what the US troops on the border are doing

A number of active-duty US troops, the first of thousands, have arrived at the US-Mexico border.

US military personnel deployed to the border ahead of the anticipated arrival of migrant caravans have started constructing bases of operations and running razor wire to prevent illegal crossings.

These photos show some of what troops are doing at the border:

(U.S. Air Force photo by SrA Alexandra Minor)

Soldiers from the the 89th Military Police Brigade, and 41st Engineering Company, 19th Engineering Battalion, Fort Riley, Kansas, arrive in Harlingen, TX on Nov. 1, 2018.

The active-duty troops which have been or will be deployed to parts of Texas, Arizona, and California are among a group of more than 7,000 troops expected to be sent to the border in support of Operation Faithful Patriot.

(U.S. Air Force photo by SrA Alexandra Minor)

Many of the engineering teams are expected to be involved in activities such as barrier construction and the hardening of key border facilities.

Active-duty military personnel are heading to the border to support the Customs and Border Protection mission.

The troops deploying to the border, according to the US military, will provide planning assistance and engineering support, as well as equipment and resources, to assist the DHS as it attempts to secure the southern border against migrant caravans from Latin America.

The number of troops slated for deployment to the US-Mexico border has risen three times in the past week, surging from several hundred into the thousands, and the number could rise again in response to operational demands.

(Angela Camara/Operation Faithful Patriot)

A C-17 Globemaster III carrying soldiers and equipment from the 63rd Expeditionary Signal Battalion, Fort Campbell, Kentucky, landed in southern Arizona on Oct. 31, 2018, in support of Operation Faithful Patriot.

There are already over 2,000 National Guard troops serving at the border, advancing the mission for Operation Guardian Support. They were deployed in April and serve in a different role than the troops presently heading south.

(Angela Camara/Operation Faithful Patriot)

Troops are bringing significant amounts of equipment for border operations, including miles and miles worth of concertina wire.

President Donald Trump, who has repeatedly characterized the approaching caravans — without evidence — as an "invasion," has warned the migrants that the military will be waiting for them when they arrive.

He has said that the total number of troops deployed to the southern border could ultimately be as high as 15,000. The president has also indicated that US troops may open fire on migrants who become aggressive.

(U.S. Army photo by Spc. Brandon Best)

A US Army soldier assigned to 309th Military Intelligence Battalion hammers a stake into the ground while setting up tents at Fort Huachuca, Arizona on Nov. 1, 2018.

The military units currently being sent to the border are acting in a Title X capacity. Military police, engineers, medical teams, airlift units, and command teams will be constructing barriers, hardening points of entry, and assisting CBP officials. These troops are not permitted to engage in law enforcement activities on US soil.

(U.S. Army photo by Spc. Brandon Best)

The Department of Defense has made it clear, despite the various claims stating otherwise, that these tent cities will house troops arriving at the border, not migrants.

While some observers argue that sending active-duty military personnel to the border is a waste of manpower, one that could costa s much as 0 million by the end of the year, the administration says troops being deployed to the border are responding to an escalated threat to US national security. As of Friday, there were around 3,500 troops deployed to staging bases along the border, the Pentagon told the Associated Press.

(U.S. Army photo by Spc. Brandon Best)

Multiple staging areas are being established at Base Support Installations, areas where troops from ten different states will set up operations.

One of the larger groups recently clashed with Mexican authorities on the border of Guatemala, a violent exchange which appears to have led President Trump to state that US troops might shoot migrants who throw rocks at US military and border patrol personnel, a position he has since backed away from.

(U.S. Air Force photo by Airman 1st Class Kristine Legate)

Airmen from the 355th Civil Engineering Squadron construct Air Force deployable airbase systems (DABS) at Davis-Monthan Air Force Base in Arizona on Nov. 1, 2018.

The migrant caravans heading north toward the US-Mexico border are currently believed to be around 800 miles away, putting them a few weeks out.

(U.S. Army photo by Sgt. Kyle Larsen)

These tents, like those set up at Fort Huachuca, will house military personnel deployed to the border in support of Operation Faithful Patriot.

In recent days, as the midterm elections come around the corner, the president has proposed eliminating birthright citizenship, denying asylum to anyone who crosses illegally, and using disproportional military force against migrants who become violent, moves and rhetoric presumably intended to highlight his administration's tough stance on illegal immigration.

(U.S. Air Force photo by SrA Alexandra Minor)

Soldiers from the 97th Military Police Brigade, and 41st Engineering Company, Fort Riley, Kansas, run 300 meters of concertina wire along the border in support of CBP operations in Hidalgo, Texas.

Critics have accused the president of engaging in a political stunt ahead of midterm elections. Secretary of Defense Jim Mattis, who approved the deployment of troops to the border in response to a DHS request, has countered such accusations, stating, "We don't do stunts in this department."

(U.S. Air Force photo by SrA Alexandra Minor)

US troops deployed with enough concertina wire already in position to cover 22 miles, with officials noting that the military had the capability to run wire along another 120 miles if necessary.

"It's all preparation in anticipation of the caravan," Manuel Padilla Jr., US Border Patrol's Rio Grande River Valley sector chief, told the Associated Press. "We're hoping that these people do not show up at the border. They're not going to be allowed in."

This article originally appeared on Business Insider. Follow @BusinessInsider on Twitter.