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.

It puts in motion plans Trump laid out in executive orders signed shortly after he took office to crack down on immigration.

Troops have assisted at the border before and will be limited to support roles unless the administration invokes the Insurrection Act.