U.S. Army soldiers of the Tactical Command Post, 1st Battalion, 15th Infantry Regiment, 3rd Heavy Brigade Combat Team, 3rd Infantry Division, monitor various communication systems during a simulated chemical attack at the National Training Center iteration 12-05, Fort Irwin, Calif., March 22, 2012. This NTC rotation provided a two-week field exercise based on force on force tactics that have not been practiced in over ten years.