The U.S. military will send more than 5,200 active duty troops to the southern border with Mexico by the end of the week, the Defense Department announced Monday.

“By the end of this week will we deploy over 5,200 soldiers to the southwest border. That is just the start of this operation; we’ll continue to adjust the numbers and inform you of those,” U.S. Northern Command and North American Aerospace Defense Command head Gen. Terrence O'Shaughnessy told reporters.

The deployment, called Operation Faithful Patriot, will be to “flow in our military with a priority to build up southern Texas, and then Arizona, and then California. . . . to harden the points of entry and address key gaps in areas around the points of entry,” O'Shaughnessy said.

The troops will support the thousands of border patrol agents already at the border as part of Operation Secure Line.

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The troops are also in addition to the 2,092 National Guard troops deployed in April to the border as part of Operation Guardian Support.

The troops will come from Fort Bragg, N.C., Joint Base Lewis–McChord, Wash., Fort Stewart, Ga., Fort Campbell, Ky., Fort Knox, Ky., and Fort Riley, Kan., among other locations.

Defense Secretary James Mattis James Norman MattisBiden courts veterans amid fallout from Trump military controversies Trump says he wanted to take out Syria's Assad but Mattis opposed it Gary Cohn: 'I haven't made up my mind' on vote for president in November MORE on Friday approved a request for assistance from the Department of Homeland Security to send the troops. The request came after President Trump Donald John TrumpBiden says voters should choose who nominates Supreme Court justice Trump, Biden will not shake hands at first debate due to COVID-19 Pelosi: Trump Supreme Court pick 'threatens' Affordable Care Act MORE ordered the military to send active duty troops to the border in response to a group of several thousand migrants traveling from Central America to the United States.

O'Shaughnessy said specific request for assistance “is for the active duty military to enhance the capacity and capabilities of [Customs and Border Protection], by providing robust military capabilities.”

He added that “as we sit right here today we have about 800 soldiers that are on their way to Texas right now,” and the soldiers deployed will be armed.

“We have the authority, given to us by Secretary Mattis — the units that are normally assigned weapons, they are, in fact, deploying with weapons,” he said.

Under the Posse Comitatus Act, federal troops are largely prohibited from engaging in domestic law enforcement activities.

Pressed by reporters as to why the Pentagon has sent active duty troops to the border given Posse Comitatus, O'Shaughnessy said the new troops will be "complementary" to the current National Guard deployment "but brings additional capability and capacity to help CBP."

"With respect to Posse Comitatus, everything that we’re doing is in line with and in adherence to Posse Comitatus," he added.

The White House earlier Monday also deflected a question on why Trump feels it’s necessary to send active duty troops to the border.

“The president’s number one job and number one priority is to protect the safety and security of Americans and he’s going to do what he deems necessary to in order to do that,” White House spokeswoman Sarah Sanders told reporters at the daily press briefing.

The military has also brought “critical material” including concertina wire “to cover up to 22 miles” and additional wire they can string for over 150 miles, O'Shaughnessy said.

The military has also brought “critical material” including concertina wire “to cover up to 22 miles” and additional wire they can string for over 150 miles.

The U.S. ground commander to head the operation is Army Lt. Gen. Jeffrey Buchanan, known for leading Hurricane Maria relief efforts in Puerto Rico last year.

O'Shaughnessy said the soldiers heading to the border include U.S. Army Corps of Engineer troops and three combat engineering battalions “with expertise in building temporary vehicle barriers” and fencing. Heavy equipment from the battalion is now on its way to Texas.

In addition, the Pentagon will send logistical support and military planning teams, medical units, military police units, command and control capabilities, three medium-lift helicopter companies to aid in transportation of CBP agents, three C-130 aircraft and a C-17 military transport aircraft.

U.S. Transportation Command (Transcom) earlier on Monday posted a video to Facebook depicting Air Force airmen loading a C-17 military transport aircraft with Army equipment “in support of Operation Faithful Patriot,” according to the post.

The announcement has already drawn swift backlash from Democrats and human rights groups, including the American Civil Liberties Union, which accused Trump of forcing the military into “furthering his anti-immigrant agenda of fear and division,” ahead of the midterm elections.

“Sending active military forces to our southern border is not only a huge waste of taxpayer money, but an unnecessary course of action that will further terrorize and militarize our border communities,” Shaw Drake, policy counsel for the ACLU Border Rights Center in El Paso, Texas, said in a statement.

“Military personnel are legally prohibited from engaging in immigration enforcement, and there is no emergency or cost-benefit analysis to justify this sudden deployment."

-Updated 6:12 p.m.