Almost all male . citizens, and male aliens living in the ., who are 18 through 25, are required to register for the military draft. However, men who currently register are not automatically inducted into military service. Currently, the United States operates its military through volunteer enlistment. The last time men were inducted into the military was during the Vietnam War. Registration for a possible future draft is required to ensure America's preparedness in the event of a military crisis. In the event of a crisis that necessitates a draft to be invoked, men would be called in sequence determined by random lottery number and year of birth. They would then be examined for mental, physical and moral fitness by the military before being deferred or exempted from military service or inducted into the Armed Forces. You may register as soon as you reach the age of 17 years and 3 months but must register within 30 days of turning 18.