Marines (21-26 Apr): 1/1 Marines, F/2/1 Marines, 3/1 Marines, 3/5 Marines, 1/11 Marines; 5th Marines (26 Apr-17 May): 1/5 Marines, 3/5 Marines, F/2/1 Marines, 1/11 Marines; SLF ALPHA (28 Apr-12 May): 1/3 Marines; 1st ARVN Rgr Grp: 21st, 37th and 39th Rgr Bns Intelligence: 3rd and 21st PAVN Rgts (2nd PAVN Div). Execution: Operation UNION marked the beginning of a bitter campaign for the control of the Que Son Basin. In mid- January 1967, Co F, 2/1 Marines had relieved an ARVN unit on Nui Loc Son to establish a modicum of control over VC/NVA access to this rice-producing area. The arrival of TF OREGON in southern I Corps in April relieved III MAF from its responsibility over the Chu Lai TAOR and freed enough forces to mount a major operation in the Que Son. On 21 Apr, F/2/1 Marines moved out of Nui Loc Son where the CP of the 1st Marines had been established and encountered strong enemy resistance at Binh Son, 4 km to the northeast. During the day, 3/1 and 3/5 Marines where helicoptered in to join the battle. At the same time, the 1st ARVN Rgr Group at Thang Binh on Route 1 pushed on foot into the valley to link up with the embattled Marines. The Marines drove the enemy out of their positions and maneuvered to force them northward but the pursuit produced only scattered contacts. By 26 Apr, the 5th Marines CP arrived at Nui Loc Son, allowing the 1st Marines to be returned to their Da Nang TAOR. On 28 Apr, SLF ALPHA landed southeast of Nui Loc Son and joined 3/5 Marines. Both battalions met only light resistance as the swept their respective areas but intelligence reports indicated that major enemy forces were still in the area. On 1 May, 1/5 Marines was inserted by helicopters 13 km east of Hiep Duc and began a sweep along the Song Chan. As the operation progressed, all three battalions had brief contacts with small enemy units, but in each case the NVA withdrew. On 10 May the Marines engaged a large and more determined enemy force entrenched on Hill 110, 4 km north of Que Son; The battle lasted until the evening of 11 May when the Marines forced the enemy to withdraw to the north. 116 NVA bodies were found but US losses were also high with 33 KIA and 135 WIA. On 13 May, 3/5 Marines engaged an enemy battalion 5 km east of Que Son, killing another 122. The last major contact of the operation took place on 15 May when Cos A and M of the 5th Marines overran a bunker complex, killing 22. Then next day, the Marines departed the valley and returned to Da Nang and Operation UNION was officially closed down on 17 May. Results: 865 enemy killed, 110 US KIA, 473 US WIA, 2 US MIA.