 A change in the Cambodian government allowed a window of opportunity for the destruction of the base areas in 1970 when Prince <unk> Sihanouk was deposed and replaced by pro @-@ US General Lon Nol . Allied military operations failed to eliminate many communist troops or to capture their elusive headquarters , known as the Central Office for South Vietnam ( COSVN ) , but the haul of captured material in Cambodia prompted claims of success . 
