The Pentagon is deploying more than 5,200 active duty troops to the southwestern U.S. border to stop caravans of migrants from crossing over illegally, U.S. officials announced Monday at a press conference.

“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,” Air Force Gen.Terrence O’Shaughnessy, commander of U.S. Northern Command and North American Aerospace Defense Command, said.

The 5,200 troops deployed under the operation, named Operation Faithful Patriot, would add to the 2,092 National Guard members already deployed to the border earlier this year. Officials confirmed that the troops who would normally carry weapons will bring their weapons with them to the border.

Officials say there are at least two migrant caravans headed to the U.S. border.

“As of this afternoon, we continue to track a large group of approximately 3,500 traveling through southern Mexico with the stated intent to reach the U.S. border,” said Kevin McAleenan, U.S. Customs and Border Protection Commissioner. He said the group was near the Chiapas-Oaxaca border in southern Mexico.

“We are also aware of a second large group of migrants at the Ciudad Hidalgo border crossing between Guatemala and Mexico. Size estimate for the second group is around 3,000,” he said.

“They’re incentivized to try to cross our border by the gaps in our legal framework, and the expectation that they will be allowed to stay. This means, at any given moment, there are tens of thousands of intending migrants between the Guatemala border and the U.S. border moving towards us.”

McAleenan said within that flow were about 17,000 criminals last year, along with “hardened smugglers” and people from over 100 different countries from around the world.

But he said the caravan phenomenon “new and challenging.”

“For the two large groups that we are following, we have already seen the first one make unlawful entry across two international borders and the second, still in Guatemala, has deployed violent and dangerous tactics against both Guatemalan and Mexican border security teams,” he said.

McAleenan said there are 26 crossing points on the southwest border, and 100 specially trained special response team operators at each location. He said there are 1,000 CBP officers ready, upon the approach of a large group at any port of entry. Between the ports of entry, there are an additional 830 Border Patrol agents ready to deploy.

U.S. troops will help the CBP transport personnel and equipment, provide engineering capabilities, medical support units, mobile housing for CBP personnel, and extensive planning support, he said.

Troops will first reinforce Texas, Arizona, and then California, O’Shaughnessy said.

The general said the troops included soldiers from three combat engineering battalions with expertise in building temporary vehicle barriers and fencing, military planning teams to work with the CBP, three medium-lift helicopter companies that can operate at night, military police units, medical units, and large aircraft that can deploy CBP personnel deploy wherever and whenever.

“We have combined command posts where our operational commanders will be working side-by-side [with the CBP] to integrate our efforts,” he said.

The first 800 troops are on their way, he said. Units deploying include The Headquarters Company, 89th Military Police Brigade, Task Force Griffin, based at Fort Hood, Texas, and the 15th Engineer Company, 19th Engineer Battalion, 20th Engineer Brigade, based at Fort Knox, Kentucky.