For gallantry in action while engaged in military operations involving conflict with an armed hostile force in the Republic of Vietnam: Sergeant Dennis K. Thatcher distinguished himself by exceptional heroism on 23 and 24 June 1971 while under continuous enemy attack at Fire Support Base Fuller and while evading the enemy to reach a friendly fire support base after evacuating Fire Support Base Fuller. On 23 June 1971, Fire Support Base Fuller came under heavy enemy attack; size of the enemy force estimated to be of regimental size plus. The enemy attacked the northeastern side of the hill, inflicting casualties on the friendly forces. During the heavy ground attack Sergeant Thatcher located himself on top of the highest bunker on the north side of the hill so he could accurately direct gunships on the advancing enemy. Even though the enemy continued to advance firing all around his highly vulnerable position, Sergeant Thatcher refused to leave until the enemy was suppressed. After approximately 4 hours, the enemy was finally halted. The enemy assaulted the hill approximately five times during the daylight hours. Each time Sergeant Thatcher occupied his position on the bunker, directing devastating suppressive fires on the enemy. At approximately 2100 hours that night the enemy mounted another attack. Even though the enemy was directing indirect fire on the northern portion of the hill, Sergeant Thatcher took up his exposed position on the bunker, using a flashlight to direct gunships firing on the advancing enemy. Sergeant Thatcher continued to flash his light even though the enemy was trying to eliminate his position. Without his direction, the enemy could not have been suppressed. During the next day, Sergeant Thatcher continued to assist the friendly forces as much as possible, moving from fighting position to fighting position, resupplying the ARVN soldiers, each time exposing himself to enemy fire. At approximately 1700 hours that day the enemy once again assaulted the hill, inflicting tremendous casualties on the friendly troops. Sergeant Thatcher again started directing air support, plus assisting the wounded soldiers. At that time the decision was made to evacuate the hill due to heavy enemy contact. Sergeant Thatcher refused to leave until he was sure most of the friendly forces were departing. He continued to aid the wounded and carry radio equipment even though he himself was physically exhausted from lack of sleep. That night the troops stayed in a field location, Sergeant Thatcher continued to aid the wounded. The next morning Sergeant Thatcher, one marine Sergeant, and eight wounded soldiers walked approximately 3000 meters of enemy infested jungle to another friendly fire base. During this dangerous walk Sergeant Thatcher personally carried wounded soldiers to an area where they could be medevaced. Sergeant Thatcher's actions were truly heroic in nature. Without his valuable assistance many friendly lives would have been lost. Sergeant Thatcher contributed immeasurably to the accomplishment of mission. His heroism is in keeping with the highest traditions of the military service and reflected great credit upon himself, his unit and the United States Army.