Must the employee give advance notice to the employer of his or her service in the uniformed services?

When is the employee excused from giving advance notice of service in the uniformed services?

Is the employee required to get permission from his or her employer before leaving to perform service in the uniformed services?

Is the employee required to tell his or her civilian employer that he or she intends to seek reemployment after completing uniformed service before the employee leaves to perform service in the uniformed services?