For conspicuous gallantry and intrepidity at the risk of his life above and beyond the call of duty while serving as a platoon sergeant of Company F in action against enemy aggressor forces. Participating in the defense of an outpost forward of the main line of resistance, S/Sgt. Guillen maneuvered his platoon over unfamiliar terrain in the face of hostile fire and placed his men in fighting positions. With his unit pinned down when the outpost was attacked under cover of darkness by an estimated force of two enemy battalions supported by mortar and artillery fire, he deliberately exposed himself to the heavy barrage and attacks to direct his men in defending their positions and personally supervise the treatment and evacuation of the wounded. Inspired by his leadership, the platoon quickly rallied and engaged the enemy in fierce hand-to-hand combat. Although critically wounded during the course of the battle, S/Sgt. Guillen refused medical aid and continued to direct his men throughout the remainder of the engagement until the enemy was defeated and thrown into disorderly retreat. Succumbing to his wounds within a few hours, S/Sgt. Guillen, by his outstanding courage and indomitable fighting spirit, was directly responsible for the success of his platoon in repelling a numerically superior enemy force. His personal valor reflects the highest credit upon himself and enhances the finest traditions of the U.S. Naval Service. He gallantly gave his life for his country.