Conscription Act

The Conscription Act is an Imperial Decree which stipulates that every able-bodied citizen who has reached their age of majority must enlist, and spend no less than two years, in the Imperial Army. The "age of majority" is the age at which a citizen is considered an adult within their culture or race. The default age is twenty in humans.
There are exceptions to this rule, of course. Those people who are pursuing careers within the Civil Service, attending an academy of higher learning such as a magical academy, or who have joined temples and dedicated themselves to Heaven.