Note: groups.jewishgen.org will be down for maintenance on Wednesday, October 5th, starting at 9AM Pacific Time (4PM Wednesday October 5, 2022 UTC), for approximately one hour.
Your best shot would be to request his service personnel record from the National Archives, as you stated. That would (potentially) include his entire military record, including postings, ships he served on, decorations and other useful administrative stuff. There was a fire in the archives in 1973 that destroyed many Army, Air Force and Marine veterans' records, but Navy veterans' records were not affected. If the veteran applied for VA benefits, you may also request a copy of his VA file under the Freedom of Information Act, by calling the VA's call center at 1-800-827-1000. If he applied for VA benefits, his VA records will most likely contain his service personnel records, as well as medical records and perhaps some personal statements made by him regarding medical issues that relate to his service. These statements may contain important service information, such as places, dates and event descriptions.
Cherry Hill, NJ, USA
Researching: Israelit/Israelite (from Novogrudok, Belarus and from Latvia), Rabinowitz (from Dyatlovo/Zhetl, Belarus), Pruss and Koifman/Kaufman (from Ukraine) and Godblat (from Belarus and Lithuania).