Be was assigned to th 111 corps

I found the reference in the Hall of Valor. He didn't serve with the U.S. III Corps (it's a Roman Numeral), because the only Corps Headquarters we sent to Vietnam was XXIV Corps.

He was an advisor to the III Vietnamese Corps, often referred to in US texts as III Corps Tactical Zone. You can read about the Corps here:

https://en.wikipedia.org/wiki/III_Corps_(South_Vietnam) 

You may also want to review "Advice and Support: The Final Years," The Army's official history of the advisory effort while your father was there. You can download it here:

https://www.history.army.mil/html/books/091/91-3/CMH_Pub_91-3-B.pdf 

Thank you so much. I never really knew which unit. He often talked of working with the local province chief. I knew he had received a Vietnamese medal for valor.  I worked alongside my father for years and he only spoke of everyday things. Never much about the action. Always said it was classified. ....... He was also among the first to meet the North Koreans and he was only 18. Talked a lot about the sacrifices his unit endured. Came back with a Bronze Star and a Purple heart.  After leaving the Army he sad that was in the past and moved on . .....Thanks again ! Any more info or direction will be appreciated.

Thank you so much. I never really knew which unit. He often talked of working with the local province chief. I knew he had received a Vietnamese medal for valor.  I worked alongside my father for years and he only spoke of everyday things. Never much about the action. Always said it was classified. ....... He was also among the first to meet the North Koreans and he was only 18. Talked a lot about the sacrifices his unit endured. Came back with a Bronze Star and a Purple heart.  After leaving the Army he sad that was in the past and moved on . .....Thanks again ! Any more info or direction will be appreciated.