The deployment of active-duty United States troops at the border with Mexico will most likely be extended through September, the Pentagon said Monday.

The Pentagon’s border mission had previously been scheduled to end on Dec. 15, and the Defense Department later extended the deployment into January. Then came Monday’s announcement.

In a rare use of military force first announced in October, the Trump administration sent about 5,900 active-duty troops to join up with Border Patrol agents and National Guard members, as a caravan of Central American migrants made its way toward the United States.

The move was viewed by many as unnecessary political fear-mongering as the midterm elections approached. Border and military officials insisted the caravan was a serious threat.