with approximately 320 killed or wounded, including more than sixty percent of the 450 troops who had assaulted into the valley. Two of its four company commanders and eight of twelve platoon leaders had become casualties. The battalion commander of the 2/506th, Lt. Col. Gene Sherron, arrived at Honeycutt's command post on the afternoon of 18 May to coordinate the relief. 3/187th was flying out its latest casualties, and its commander had not yet been informed of the relief. Before any arrangements were made, Zais landed and was confronted by Honeycutt, who argued that his battalion was still combat effective. After a sharp confrontation, Zais relented, although he assigned one of Sherron's companies to Honeycutt as reinforcement for the assault. Final assault Two fresh battalions, the 2/501st Infantry and ARVN 2/3d Infantry, were airlifted into landing zones northeast and southeast of the base of the mountain on 19 May. Both battalions immediately moved onto the mountain to positions from which they would attack the following morning. Meanwhile, the 1/506th for the third consecutive day struggled to secure Hill 900. The 3rd Brigade launched its four-battalion attack at 10:00 on 20 May, including two companies of the 3/187th reinforced by Company A 1/506th. The attack was preceded by two hours of close air support and ninety minutes of artillery preparatory fires. The battalions attacked simultaneously, and by 12:00 elements of the 3/187th reached the crest, beginning a reduction of bunkers that continued through most of the afternoon. Some PAVN units were able to withdraw into Laos, and Hill 937 was secured by 17:00. ARVN participation The ARVN 2nd Battalion, 3rd Regiment, 1st Division participated in the battle. Author Andrew West wrote in 2007, particularly based on the statements by General Creighton W. Abrams in "The Abrams Tapes," says its role in the final assault was as follows: The unit was positioned on a stretch of the PAVN defense line that was lightly defended, and sent a scout party to test the forward enemy lines earlier than the proposed assault time; this party was quickly able to discern the minimal enemy strength. The 2/3 commanding officer decided to exploit the situation, and attack in advance of the other units. The 2/3 reached the crest of Hamburger Hill around 10:00, ahead of the 3/187th, but was ordered to withdraw from the summit because allied artillery was to be directed on to the top