If this isn't the correct subreddit, I appologize. My grandpa had a lot of stories of his wartime career, but he wasn't very forward when it came to sharing them. He passed not long ago and I'd like to learn more. About all we know is that he worked with OSS, he was in north Africa, he was in the 2nd wave at D-day (beaches were secured but he saw the red water), and that he was trapped behind enemy lines for an indeterminate amount of time. I'd like to find reports, and hopefully learn something of what he did with OSS. But where would I even start? Any help is appreciated. Thank you.
The National Archives is probably the best place for you to start your search: http://www.archives.gov/veterans/
From there you can do some online sleuthing, as well as find out what you'll need to request a copy of your grandfather's service records. You'll probably want to start by requesting his DD Form 214 (separation of service form), which will list all of the details of his service, including medals awarded, promotions, campaigns participated in, etc. You will probably need to have someone else request the records (your grandmother, if she's still living), as I believe that they must be requested by the next-of-kin. I seem to remember running into that problem while requesting my own grandfather's records.
Good luck!
[edit] You may want to x-post this to /r/Genealogy, too.