Corporal Steven Cary, a chemical, biological, radiological, nuclear defense specialist with 1st Marine Division, takes a sample of a simulated poisonous liquid that a terrorist might use to harm civilians during a mock poisonous gas attack during Urban Shield 2014 in the San Francisco Bay Area, Calif. Urban Shield is a four-day event that brings together local, regional and federal law enforcement agencies to include U.S. military service members as well as detachments from allied nations to share tactics and best practices in crisis response.