 The objective of the campaign was the defeat of the approximately 40 @,@ 000 troops of the People 's Army of Vietnam ( PAVN ) and the National Front for the Liberation of South Vietnam ( NLF , also known as Viet Cong ) who were <unk> in the eastern border regions of Cambodia . Cambodia 's official neutrality and military weakness made its territory effectively a safe zone where Vietnamese communist forces could establish bases for operations over the border . With the US shifting toward a policy of Vietnamization and withdrawal , the US sought to shore up the South Vietnamese government 's security by eliminating the cross @-@ border threat . 
