sentences:  On 23 April the 147th Marine Brigade returned to Ái Tử and the 258th Marine Brigade redeployed to Huế leaving its 1st Battalion at Firebase Pedro under the control of the 147th Brigade.On 28 April the commander of the 20th Tank Battalion withdrew from Đông Hà to deal with a PAVN force threatening Ái Tử Combat Base, seeing the tanks leaving the soldiers of the 57th Regiment panicked and abandoned their positions leading to the collapse of the ARVN defensive line.The 7th Marine Battalion was sent to Ái Tử to help defend the base.