According to the Veterans' Preference  website, "veterans who are disabled, who served on active duty in the Armed Forces during certain specified time periods or in military campaigns are entitled to preference over others in hiring for virtually all federal government jobs." The website contains links to a fact sheet, brochure, and legal briefing that provide general information on the program and describe eligibility. For more specific information on Veterans' Preference, download the PDF file Veterans' Preference Operations Manual , which explains how the federal employment system works and how Veterans' Preference and the special appointing authorities for veterans operate within the system.
To file a Veterans' Preference Federal employment claim, contact the VETS' office  located in your state.
-  Veterans' Preference
-  Veterans' Preference Operations Manual
-  VETS' office