[drpix]

If we're not speaking of offshore on naval vessels, here's the numbers:

Allied Troop Levels - Vietnam

Year    American
1964	23,300
1965	184,300
1966	385,300
1967	536,100
1968	475,200
1970	334,600
1971	156,800
1972	24,200
1973	50

americanwarlibrary.com

The last combat troops were gone in 1972 and the last combat operations ended even earlier - with the USMC leaving before the Army.

[UnwashedPeasant]

"Allied Troop Levels - Vietnam

Year   American
1964   23,300
1965   184,300
1966   385,300
1967   536,100
1968   475,200
1970   334,600
1971   156,800
1972   24,200
1973   50

americanwarlibrary.com"

That aligns with the claim of service from 1972 to 1976.

The man is clearly mentally ill or dishonest, but he certainly might be a vet.