Short Answer 
The Vietnam War primarily used a draft system to recruit soldiers, resulting in a diverse demographic primarily composed of young men around nineteen years old, many from working-class backgrounds. A considerable number of these soldiers were African American, highlighting socio-economic and racial issues during the war.
Step 1: Understand the Draft System
The majority of military personnel in the Vietnam War were recruited through a draft system. This means that rather than enlisting voluntarily, many young men were selected to serve in the military. This process led to a diverse group of individuals being sent to fight in Vietnam, impacting their backgrounds and demographics.
Step 2: Recognize the Average Age and Background
The average age of infantry soldiers during the Vietnam War was around nineteen years old. This young age reflects that many soldiers were teenagers or barely past adolescence. Additionally, most of these soldiers came from the working class, meaning they had limited economic resources and opportunities prior to being drafted.
Step 3: Acknowledge Racial Demographics
In the Vietnam War, a significant portion of the soldiers were African American. This demographic detail sheds light on the socio-economic factors at play during the war, highlighting issues of race and class. Understanding these aspects provides a deeper insight into the experiences and challenges faced by those who served.