A more thorough explanation:

Definition: Enlistment is the act of voluntarily joining a branch of the armed services.

Example: John decided to join the army after graduating from high school.

Explanation: In this example, John made a voluntary decision to join the army. This is an example of enlistment.

Example: The navy is offering signing bonuses for new enlistments.

Explanation: In this example, the navy is encouraging people to voluntarily join by offering bonuses. This is another example of enlistment.