 On 18 December 1967, following their intensive training, soldiers of the PAVN 41st Special Forces Battalion launched the first phase of their operation by conducting terrain reconnaissance and watching activities on Lima Site 85 to learn their opponent's routines.As part of the second phase, commenced on 22 January 1968, six PAVN sappers were sent out to climb Phou Pha Thi, to pinpoint opposing positions in and around Lima Site 85, as well as routes of withdrawal.On 28 February 1968, the PAVN Special Forces completed their preparations, and they began marching towards their assembly point on 1 March.