 Thieu then authorized Operation Cuu Long , in which ARVN ground forces , including mechanized and armoured units , drove west and northwest up the eastern side of the Mekong River from 9 May – 1 July . A combined force of 110 Vietnamese Navy and 30 U.S. vessels proceeded up the Mekong to Prey Veng , permitting IV Corps ground forces to move westward to Phnom Penh and to aid ethnic Vietnamese seeking flight to South Vietnam . Those who did not wish to be repatriated were then forcibly expelled . Surprisingly , North Vietnamese forces did not oppose the evacuation , though they could easily have done so . 
 Thieu then authorized Operation Cuu Long , in which ARVN ground forces , including mechanized and armoured units , drove west and northwest up the eastern side of the Mekong River from 9 May – 1 July . A combined force of 110 Vietnamese Navy and 30 U.S. vessels proceeded up the Mekong to Prey Veng , permitting IV Corps ground forces to move westward to Phnom Penh and to aid ethnic Vietnamese seeking flight to South Vietnam . Those <a href='null_relcl' title='1'><mark>who</mark></a>did not wish to be repatriated <a href='uninflect' title='2'><mark>were</mark></a> then forcibly expelled . Surprisingly , North Vietnamese forces did not oppose <a href='None' title='3'><mark>the</mark></a><a href='negative_concord' title='4'><mark>evacuation</mark></a> , though they could easily have done so . 
Thieu then authorized Operation Cuu Long , in which ARVN ground forces , including mechanized and armoured units , drove west and northwest up da eastern side of the Mekong River from 9 May – 1 July . A combined force of 110 Vietnamese Navy and 30 U.S. vessels proceeded up the Mekong to Prey Veng , permitting IV Corps ground forces to move westward to Phnom Penh and to aid ethnic Vietnamese seeking flight to South Vietnam . Those did not wish to b repatriated was then forcibly expelled . Surprisingly , North Vietnamese forces did not oppose no evacuation , though they could easily have done so .