U.S. Army soldiers, from Charlie Company, 1st Battalion, 21st Infantry Regiment, 2nd Stryker Brigade Combat Team, 25th Infantry Division, "Gimlets" detonate an M67 hand grenade prior to entering trench obstacle Sept. 20, 2012, during a live fire exercise at the Pohakuloa Training Area, on Hawaii's Big Island. Soldiers from the 1st Battalion, 21st Infantry Regiment, are conducting a month-long exercise which is focused on platoon level collective training with enabler integration. The training will culminate in a combined arms live fire exercise later this month.