Dear Mr. Davis,
Thank you for posting your request to History Hub!
It is difficult to prove a negative. We suggest that you request an Official Military Personnel File (OMPF) for your father. While National Personnel Records Center can not certify that a person did not serve in the military, they can provide the results of a search for relevant records based on the information you provide them. To request a search, download a Standard Form 180, fill it out and mail it to the National Personnel Records Center, (Military Personnel Records), 1 Archives Drive, St. Louis, MO 63138-1002 or fax it to 314-801-9195. When filling out the form, provide as much information as you have about your father, such as his full name, social security number (if applicable), date of birth, place of birth, and date of death. Where it asks you to give the branch of service, dates of service, and service number write “unknown.”
If your father registered for the draft prior to 1976, you can request his Selective Service Records from the National Archives at St. Louis. You can also search the World War II Army Enlistment Records which are available online through Access to Archival Databases (AAD). These records cover the US Army (to include the Army Air Force) but do not include records of service in the Navy, Marine Corps or Coast Guard.
We hope this information is helpful. Best of luck with your family research!