Need help identifying what exactly this civil war letter talks about:?

The letter is nearly illegible form this angle. It seems that it is dated July 27, 1831, thirty years before the Civil War.

From the few words I could make out the person who wrote the letter is resigning his commission as a Colonel in the in the 199th infantry regiment of New York State Militia.

How about taking a picture straight on, not at an angle, and focused better?

I doubt if anyone can give you an answer because it's not possible to read the letter. Perhaps you could transcribe the letter and add that to your question.