1960s: The United States military drafts about 1.8 million young men to serve as soldiers during the Vietnam War. A man can qualify for a student deferment from the draft if he is a fulltime student and able to show satisfactory progress toward a degree.

Today: The United States no longer relies on the draft but fills the ranks of its military with volunteers of both genders. However, men between the ages of eighteen and twenty-five must still register with the Selective Service System in case of a national military emergency.

1960s: About 80 percent of those fighting in the Vietnam War are from working-class or poor backgrounds. There are disproportionately high numbers of African Americans serving as combat troops.

Today: In the all-volunteer Unites States military, minorities account for nearly 35% of the personnel, and African Americans account for 20%.

1960s: On April 15, 1967, more than 200,000 protesters gather...