On 27 July, the ARVN Marine Division was ordered to relieve the Airborne units as the lead element in the battle. But progress was slow, consisting of vicious house-to-house fighting and incessant artillery barrages by both sides. In September, the final assault to capture the heavily defended citadel was launched; it was finally taken on 16 September. Trưởng's forces then advanced to the southern bank of the Thach Han River, where they halted, exhausted and depleted by heavy casualties and unable to push on to Đông Hà.