On 13 May with intensive air support the 31st Regiment finally overran the PAVN positions and extended ARVN control to 8 km north of Chơn Thành. The 32nd Regiment then deployed into the Tau O area () a further 5 km north, where they ran into the 209th Regiment's well-prepared blocking positions, which stopped the division's advance for 38 days despite extensive artillery and air support, including B-52 strikes. This stalemate would continue until the PAVN withdrew from An Lộc. On 15 May a task force of the 15th Regiment, 9th Division, which was redeployed from the Mekong Delta, and the 9th Armored Cavalry Squadron, 21st Division moved north, east of Route 13 bypassing the Tau O roadblock to establish a fire support base at Tan Khai () 10 km south of An Lộc. On 20 May the PAVN 141st Regiment attacked the base at Tan Khai and continued attacking unsuccessfully for three days against a determined defense before withdrawing. In mid-July the 21st Division was replaced by the 25th Division and it completed the destruction of the remaining PAVN strongpoints at Tau O by 20 July.