Company D, 16th Armor, 173rd Airborne Brigade was the first U.S. Army armor unit deployed to Vietnam. It originally consisted of three platoons of M113s and a platoon of 90mm M56 Scorpion self-propelled anti-tank guns (SPAT). It was the only independent armor company in the history of the U.S. Army. Upon the company's arrival in Vietnam, a fourth line platoon was added; this was equipped with M106 4.2 in. mortar carriers (modified M113s). The mortar platoon often operated with Brigade infantry units to provide indirect fire support. It also deployed at times as a dismounted infantry unit. The remaining SPATS platoon was reequipped with M113s in late 1966 and the mortar platoon was deactivated in early 1967. From early 1967, D/16th had three line platoons equipped with M113s and eventually, its diesel version, the M113A1. It also standardized in late 1968 with three machine guns per track, one M2 .50 caliber and two M60 machine guns mounted on each side. After several years, the machine gun array varied considerably from APC to APC. The company conducted search and destroy missions, road and firebase security. Twenty-five D/16th paratroopers were killed in action and many more were wounded during the course of the war. D Company's largest battle took place on 4 March 1968 at North Tuy Hoa. "During the day, the company lost 5 men killed, 16 wounded, and 3 missing (who are believed dead as two unrecogizable bodies were found). The enemy took a much greater loss. An estimated 2 enemy battalions, 85th Main Force (VC) and the 95th NVA Regiment, were rendered ineffective as they had 297 KIAs, with D/16th Armor receiving credit for killing 218." The revised official count for D/16 was 8 KIA and 21 WIA. The company commander, Captain Robert Helmick, was awarded the DSC, and many D/16th soldiers earned awards for valor. D Company, 16th Armor was awarded a Meritorious Unit Award for its actions in Vietnam. It was deactivated in 1969 and the company's M113s were distributed to E Company, 17th Cavalry, 173rd Airborne Brigade.