The Pentagon announced Wednesday that Acting Defense Secretary Richard Spencer approved a request from the Department of Homeland Security to send an additional 1,000 active duty troops and 1,000 Texas National Guard troops to the nation’s southern border.

The active duty deployments will consist of approximately 1,100 troops providing the U.S. Customs and Border Patrol with aerial surveillance, operational, logistical, and administrative support.

The Pentagon first began sending active duty troops to the border last fall ahead of several migrant caravans from Central America making their way to the border. The active duty troops supplemented a separate mission by National Guardsmen to support border security.

The active duty troops on this deployment are meant to provide a “backfill” due to a shortfall in volunteer National Guard personnel, the Pentagon said.

The 1,000 Texas National Guard troops are deploying with the consent and under the command of Texas Governor Abbott, the Pentagon said.

Approximately 750 of the National Guard troops will provide supplemental holding support to CBP at its temporary adult migrant holding facilities in Donna, Texas, and Tornillo, Texas, the DOD said.

They will also assist DHS law enforcement personnel with operational, logistical, and administrative support. Migrants will continue to be supervised by DHS law enforcement personnel, not military personnel, the DOD said.

Approximately 250 National Guard troops will support at CBP ports of entry and airports to enhance border security and improve the flow of commercial traffic, the DOD said.

The Pentagon said that DHS will provide the National Guard troops with force protection and mission specific training.