More than 5000 troops have been deployed to the border, mainly to build barriers to harden points of entry. Most troops are scheduled to leave the border within weeks.
As a group of migrants continues to make its way to the U.S.-Mexico border at Tijuana, the Marines are fortifying the two Ports of Entry in San Diego.
At the Otay Mesa Cargo Facility, Marines are topping the existing border wall with another two rows of concertina wire. The Marines are mainly engineers.
Special Purpose Marine Air-Ground Task Force 7 is made up mostly of Marines from Camp Pendleton, but also from Marine Corps Air Station Miramar and 29 Palms. They have been working along the border for more than a week, building barriers and laying concertina wire to harden the ports of entry in San Diego.
"We construct this wall," said 2nd Lt. Dustin Pavlick, who is stationed at Camp Pendleton. "Work on this wall and construct these obstacles and that's pretty much it, sir. That's our job. That's our mission and the mission has priority right now."
The Marines are staying in tents at the border. They have been given few details of the operation beyond what they do each day.
Marines are also providing air support for the Immigration and Customs Enforcement. The Marines working around the ports of entry are not armed. They are guarded by Army military police from Fort Bliss.
The MPs are the only troops who are supposed to be armed under the Department of Defense border support mission. The soldiers are not supposed to engage anyone crossing the border unless they or the Marines are under threat.
The Army's Northern Command is running the operation. Army spokesman Capt. Guster Cunningham III said the troops are along the border to support Homeland Security, not enforce the law.
Instead, most of the 1,100 Marines are building barriers. That includes the busy San Ysidro Port of Entry, where Marines put in place concrete barriers topped with rows of concertina wire.
They also closed three vehicle lanes. Drivers in line said the narrowed entry created a backup that was more than 2 hours long Friday morning.
Approximately 5,900 troops have been deployed along the southern border, including 2,800 in Texas, more than 1,500 in Arizona and a total of 1,500 troops in California, according to U.S. Northern Command said. The operation is scheduled to go until Dec. 15.