I don't know how you can say that. There were no "front lines" in Vietnam....
Don't believe what you read on the internet or see on TV. Most of those who served in Vietnam lived a relatively safe and routine life. They were safely ensconced on a secure base and provided administrative and logistics support to the war. A small minority lived "outside the wire" and fought, not the Viet Cong, but the Regular North Vietnamese Army. But all of them were in the combat zone and were expected to defend themselves and to contribute to the fight if required. The guys behind the wire did not want to wander out there in bad guys country. The guys out in the bush wished that they had learned how to type.
These people are called Vietnam Veterans. Blumenthal is not among them.