 The 31st Regiment was then lifted by helicopters 6km north of Chơn Thành where it fought the PAVN 165th Regiment, 7th Division, later reinforced by the 209th Regiment, for the next 13 days.On May 11, 1972, the PAVN launched a massive all-out infantry and armor (T-54 medium tanks) assault on An Lộc.The attack was carried out by units of the 5th and 9th PAVN divisions.