Commissioner of Customs and Border Protection Alan Bersin responds to questions from members of the press during a Pentagon press briefing on July 19, 2010. The principle topic of the briefing was the mission of 1,200 National Guard troops who will begin deployments along the U.S.-Mexico border. Also participating in the briefing are Chief of the National Guard Bureau Gen. Craig McKinley, U.S. Air Force, and Director of Immigration and Customs Enforcement John Morton.