 In December 1967, a communist military offensive in the region was signalled by a series of skirmishes.On 15 December, CIA-led Hmong reconnaissance patrols detected both PAVN and Pathet Lao battalions moving against Nam Bac, at the time the stronghold of the Royal Lao Army.On 16 December, two Pathet Lao companies overran Phou Den Din, only east of Lima Site 85.