USERRA establishes the cumulative length of time that an individual may be absent from work for military duty and retain reemployment rights to five years. The exceptions to the five-year limit include initial enlistments lasting more than five years, periodic United States National Guard and reserve training duty, and involuntary active duty extensions and recalls, especially during a time of national emergency. USERRA clearly establishes that reemployment protection does not depend on the timing, frequency, duration, or nature of an individual's service as long as the basic eligibility criteria are met.