 Then, in an attempt to fool Hmong and US intelligence, the North Vietnamese made diversionary movements against Muong Son to cover their main assault.On 9 March, elements of the PAVN 41st Special Forces Battalion arrived in the vicinity of Phou Pha Thi, where they made final preparations for their assault.By 9 March 1968, the US facility atop Phou Pha Thi was surrounded by PAVN and Pathet Lao units.