 The feasibility of the plan came into question, however, when the last contact with the Da Trach defenders on 19 July revealed that the command group and two companies of the 78th Rangers were under heavy attack on the hill at Cua Tan.After seizing Da Trach, the PAVN placed infantry battalions and antiaircraft guns in the hills above the valley, awaiting the arrival of the ARVN 2nd Infantry.The RVNAF struck hard at these forces on the 18th and 19th and caused heavy casualties, but the PAVN could not be dislodged.