The Gulf of Tonkin is a body of water that lies on the East Coast of North Vietnam and the West Coast of the island Hainan.

It's a staging area meaning close enough for the US to deploy air support. Far enough away to avoid enemy fire.

From what I know of the times speaking to Vets and watching Good Morning Vietnam. A lot of news was censored and kept from US soldiers.

He was in the Vietnam Conflict Arena but not on the actual soil.