The President of the United States of America takes pleasure in presenting the Silver Star to First Lieutenant Andrew F. O’Sullivan (MCSN: 0-105219), United States Marine Corps Reserve, for conspicuous gallantry and intrepidity in action while serving as Fire Support Coordination Officer with the First Battalion, Fourth Marines, THIRD Marine Division, in connection with combat operations against the enemy in the Republic of Vietnam. On 20 March 1969, First Lieutenant O’Sullivan landed with the first wave of assault helicopters at Landing Zone ARGONNE and immediately came under intense rocket-propelled grenade and automatic weapons fire from a well-entrenched North Vietnamese Army force. Rapidly establishing a fire support coordination center, he began directing artillery fire against the hostile emplacements. With complete disregard for his own safety, he repeatedly moved across the fire-swept terrain to vantage points where he could more effectively observe and adjust his supporting fire. As a result, the enemy fire was suppressed sufficiently to enable helicopters to land with supplies and to evacuate the wounded. Throughout the night, he remained on watch to arrange for night defense fires, improve his communications, and plan and direct countermortar fires. When the Marines’ position came under a heavy hostile mortar barrage the following morning, he left his covered position and fearlessly moved across the hazardous area to a position where he could more accurately direct artillery fire. Observing the mortar platoon commander fall wounded, First Lieutenant O’Sullivan, despite his lack of experience with mortars, immediately assumed command of the platoon and ably directed and assisted in delivering a steady volume of mortar fire against the enemy, and simultaneously shouting instructions to his radio operator on relaying corrections for the artillery missions being fired. Although wounded, he ignored his own painful injuries as he directed a 106-mm. recoilless rifle crew to fire flechette rounds into an area from which North Vietnamese small arms fire was being received. When informed of the loss of some key officers, First Lieutenant O’Sullivan, refusing medical evacuation, resolutely remained with his unit through the battle for the landing zone and skillfully controlled actions in the combat operations center. His superb leadership and indomitable fighting spirit inspired all who observed him and contributed significantly to securing the vital landing zone. By his courage, bold initiative and unwavering devotion to duty in the face of great personal danger, First Lieutenant O’Sullivan upheld the highest traditions of the Marine Corps and of the United States Naval Service.