Two US Army soldiers assigned to Headquarters and Headquarters Battery, 32nd Battalion, 31st Air Defense Artillery Brigade, head for cover after a simulated aerial chemical attack against their camp on McGregor Range, Fort Bliss, Texas. The (Not Shown) chemical attacks are executed by Russian helicopters operated by members of the Opeational Test and Evauation Command, Threat Support Activity, Biggs Army Airfield, TX in support of Exercise ROVING SANDS '97, 21 April 1997