At midday on 23 March the last ARVN units had crossed the border and reached the forward positions of U.S. units in South Vietnam. Due to the PAVN armored threat the U.S. 1st Battalion, 77th Armor Regiment was moved to the border to engage any PAVN tanks. During the day U.S. air support included 756 helicopter gunship sorties, 238 tactical airstrikes and 11 B-52 strikes. On the morning of 24 March U.S. air cavalry sighted PAVN armored vehicles at five different locations near Route 9 on the Laotian side of the border. Helicopter gunships and tactical airstrikes destroyed ten tanks. At FSB Hotel the PAVN began probing the perimeter and General Khang ordered its withdrawal rather than repeat the fighting at FSB Delta. That afternoon U.S. helicopters extracted the 258th Marine Brigade and all of their artillery which were redeployed to Lang Vei to establish a firebase covering the border area.