Employees who engage in such active or inactive roles in the US military, like the National Guard and Reserve of the Armed Forces, are entitled to take a leave of absence from work under the military leave program. Employees who quit a civilian job for military service, whether voluntary or compulsory, have the legal right to return to their previous work.
Related: Bereavement Leave, Disability Leave, Sick Leave Pay, Family and Medical Leave Act of 1993 (FMLA)