The ARVN 4th Mechanized Rifle Squadron was then deployed to rescue the South Vietnamese soldiers and US aircrews who were trapped at the southwest end of Ap Bac, but its commander was highly reluctant to move heavy M113 APCs across the local terrain. Ultimately, their presence made little difference as the VC stood its ground and killed more than a dozen South Vietnamese M113 crew members in the process. Late in the afternoon, the ARVN 8th Airborne Battalion was dropped onto the battlefield and, in a scene that characterized much of the day's fighting, were pinned down and could not break the NLF's line of defense. Under the cover of darkness the VC withdrew from the battlefield, having won their first major victory.