Texas Gov. Greg Abbott deployed the troops to the Rio Grande Valley, where he said they'll work side-by-side with U.S. Border Patrol agents to keep migrants from illegally entering the country. Some of those troops left from the U.S. Naval Air Station Joint Reserve Base in Fort Worth Monday morning. The others left from a base in Houston.

Texas Gov. Greg Abbott (R) is sending hundreds of soldiers in the Texas Military Department to work with the U.S. Border Patrol in the Rio Grande Valley.

That policy change was made official Sunday after Abbott and Pete Flores, the acting commissioner of U.S. Customs and Border Protection, signed a memorandum of understanding that grants Guard troops the expanded authority.