Dear Mr. Keane,
Thank you for posting your request on History Hub!
If the individual enlisted in the US Army between ca. 1938 and 1946, there may be a record of him in the database World War II Army Enlistment Records that is available using the Access to Archival Databases (AAD). Please be advised that there are gaps in these records.
If he was an enlisted sailor in the U.S. Navy, there may be a listing for him in the Muster Rolls of U.S. Navy Ships, Stations, and Other Naval Activities, 1/1/1939 - 1/1/1949 in the Records of the Bureau of Naval Personnel (Record Group 24). As part of our on-going commitment to preserve our records, the National Archives has entered into partnership with Ancestry.com to digitize some of NARA's holdings. Digitized records include Muster Rolls/Personnel Diaries (crew rosters) of U.S. Naval Ships and Stations for the dates of January 1,1941 thru January 1, 1949. These records are now available in digital form and can be viewed online as the data collection U.S. World War II Navy Muster Rolls, 1938-1949. If you find a result for him in Ancestry, be sure to select the option to view the original record, as it typically includes the serial number of the sailor next to his name.
In response to the COVID-19 pandemic, the National Archives has partnered with Ancestry to make the vast majority of their NARA-digitized holdings freely available to the public. Anyone with Internet access may create an account, access NARA records, and use other Ancestry resources, such as their educational offerings and family tree-maker application. For more information see Ancestry’s announcement -- “Free At-Home Education Resources From Ancestry® and Access to Nearly 500M National Archives Records”.
Lastly, we suggest that you request a copy of his Official Military Personnel File (OMPF). OMPFs and individual medical reports for those who served in the U.S. Armed Forces and who were separated from the service prior to 1958 are in the custody of NARA's National Personnel Records Center in St. Louis. In many cases where Army and Army Air Corps personnel records were destroyed in the 1973 fire, proof of service can be provided from other records such as morning reports, payrolls, and military orders, and a certificate of military service will be issued. Navy and Marine Corps OMPFs were not affected by the fire. Please complete a GSA Standard Form 180 and mail it to NARA's National Personnel Records Center, (Military Personnel Records), 1 Archives Drive, St. Louis, MO 63138-1002. Veterans and their next of kin can also use eVetRecs to request records. See eVetRecs Help for instructions. If there is any information requested by the SF-180, such as the serial number, which you do not know, you can leave this blank. However, the more information you provide, the easier it will be for NPRC staff to locate the correct file. For more information see Official Military Personnel Files (OMPF), Archival Records Requests.
Due to the coronavirus public health emergency, the National Personnel Records Center is servicing only urgent requests related to homeless veterans, medical emergencies, and funerals which may be faxed to 314-801-0764. We thank you for your patience and look forward to resuming normal operations when the public health emergency has ended.
We hope this is helpful. Best of luck with your family research!