For heroism in ground combat against a hostile force in the Republic of Vietnam on 3 April 1969. Sergeant Lambert distinguished himself while serving as a squad leader in Company A, 2nd Battalion, 501st Infantry, on a reconnaissance in force operation in the A Shau Valley, Republic of Vietnam. While on a break his platoon set up security on a nearby ridge line. During his break he noticed two North Vietnamese soldiers creeping up a narrow trail to his front. The enemy simultaneously saw Sergeant Lambert and levelled hurried fire in his direction. The enemy soldiers then turned and ran into the thick brush alongside the trail. He immediately plunged into the brush in pursuit of the two assailants and was wounded by the initial enemy fire but managed to return the fire. Moving forward again, he discovered one of the North Vietnamese dead and a blood trail leading into the surrounding brush. After a brief search for the wounded enemy soldier, he heard gunfire coming from his platoon's break area. He crawled back to his platoon to find it pinned down by an undetermined number of North Vietnamese. Despite his wound, he then played a prominent role in repulsing the enemy assault. Sergeant Lambert's personal bravery and devotion to duty were in keeping with the highest traditions of the military service and reflect great credit upon himself, his unit, and the United States Army.