 The Vietnam War , was a conflict between the Democratic Republic of Vietnam ( DRVN , DRV or North Vietnam ) and the Republic of Vietnam ( RVN or South Vietnam ) , which eventually involved their respective allies . In 1959 , the United States sent military advisors to train the Army of the Republic of Vietnam . By 1965 , there were 25 @,@ 000 military advisors in South Vietnam and on March 8 , 1965 , the United States Marines became the first US combat troops to land in South Vietnam , with a force of 3 @,@ 500 . 
 The Vietnam War , was a conflict between the Democratic Republic of Vietnam ( DRVN , DRV or North Vietnam ) and the Republic of Vietnam ( RVN or South Vietnam ) , which eventually involved their respective allies . In 1959 , the United States sent military advisors to train the Army of the Republic of Vietnam . By 1965 , <a href='dey_it' title='1'><mark>there</mark></a> <a href='uninflect' title='2'><mark>were</mark></a> 25 @,@ 000 military advisors in South Vietnam and on March 8 , 1965 , the United States Marines became the first US combat troops to land in South Vietnam , with a force of 3 @,@ 500 . 
The Vietnam War , was a conflict between the Democratic Republic of Vietnam ( DRVN , DRV or North Vietnam ) and the Republic of Vietnam ( RVN or South Vietnam ) , which eventually involved their respective allies . In 1959 , the United States sent military advisors to train the Army of da Republic of Vietnam . By 1965 , it was 25 @,@ 000 military advisors in South Vietnam and on March 8 , 1965 , tdaUnited States Marines became thdairst US combat troops to land in South Vietnam , with a force of 3 @,@ 500 .