By 18 March the PAVN were well aware of the South Vietnamese withdrawal and they began concentrating forces near FSB A Luoi and FSB Delta. At Delta the PAVN had moved anti-aircraft guns in close to the base and were pounding it with artillery fire and so the 2nd and 4th Marine Battalions patrolling to the south were withdrawn to secure the area around the base and prepare for withdrawal. At midday the 1st, 2nd and 3rd Battalions, 1st Infantry Regiment withdrawing from the Lolo area were lifted from an area 2km southwest of FSB A Luoi and flown back to Khe Sanh. The 5th Battalion, 2nd Infantry Regiment was lifted from LZ Brown. That night the 2nd, 3rd and 4th Battalions, 2nd Infantry Regiment near LZ Brown came under attack from the PAVN with artillery fire followed by ground assaults. That night General Lãm called a meeting of his Division commanders at Khe Sanh and they all recommended speeding up the withdrawal to avoid units being cut off. Following the meeting Lãm ordered the withdrawal accelerated and that plans begin for extracting the 2nd Infantry Regiment from LZ Brown and FSB Delta 1.