Defense Secretary Jim Mattis traveled to Texas to the U.S.-Mexico border to meet with some of the estimated 5,900 active-duty U.S. troops deployed there in support of the Department of Homeland Security.

The border deployment aims to provide additional capability and capacity to U.S. Customs and Border Protection in reinforcing points of entry and shoring up the border with concertina wire and other barriers. The capabilities include engineering battalions, military police, planning teams, integrated command and control, aviation, medical and logistics assets.

On his Nov. 14 visit, Mattis told reporters the situation is “dynamic” and could lead to additional requests for support. He predicted the work the active-duty troops have been asked to perform would be complete “probably within a week to 10 days.” The deployment is authorized through mid-December, but the Army is planning for a possible extension.

Joining more than 2,000 National Guard troops already on the border, soldiers from Fort Campbell and Fort Knox, Ky., began deploying for the Texas border in late October, and others have since deployed to border zones in Arizona and California.

The deployment of active-duty troops was ordered by President Donald Trump in response to a northward march by thousands of Central Americans seeking to enter the U.S.