In early February 1971 , 16,000 ( later 20,000 ) ARVN troops rolled across the Laotian border along Route 9 .
In early February 1971 , 16,000 ( later 20,000 ) ARVN troops headed for the PAVN logistical center at Tchepone .
In early February 1971 , 16,000 ( later 20,000 ) ARVN troops rolled across the Laotian border along Route 9 and headed for the PAVN logistical center at Tchepone .