The Pentagon’s Transportation Command will use military aircraft to send more than 5,000 undocumented immigrants from San Diego and El Paso, Texas, who are detained by Customs and Border Protection, Acting Defense Secretary Robert Salesses said in a statement. The troops also will assist in building new border fences and barriers.

Acting Defense Secretary Robert Salesses said the troops will fly helicopters to assist Border Patrol agents and help in the construction of barriers.

The Pentagon said Wednesday it has begun deploying 1,500 active-duty troops to the southern border, putting in motion plans President Trump laid out in executive orders shortly after he took office to crack down on immigration.

The Pentagon will send 1,500 active-duty troops to the southwestern border by the end of the month, a Defense Department official said on Wednesday, helping to fulfill one of President Trump’s main goals to stem the flow of migrants into the United States.