Twenty nine tactical teams, including three international, participated in Urban Shield 2010, the nation's largest first-responder training hosted by the Alameda County (Calif.) Sheriff's Office. Organizers roll out scenario-based exercises at a variety of venues that teams must respond to during a 48-hour period. With each exercise, the teams must manage and respond to an ongoing critical incident. The exercises "provide opportunities to enhance response efforts and identify training needs in a simulated environment," according to organizers. Photos courtesy of Alameda County Sheriff's Office.