Patrick, I'd love to see the jpg image and, with your permission, I'll upload it to the internet and include it in a post so everyone can see it. You can email it as an attachment to:
I don't see a single person named Johnson in the 2nd Creek Mtd Rifles. There are several persons named Johnson in the 1st Rgt but no "G.N.". I also looked at the 1860 Census of Arkansas and whites in the Creek Nation -- there was a Madison Johnson (born in Virginia) working as a carpenter in the Creek Nation in 1860.
In brainstorming about our mystery man, a couple of things came to mind.
It would seem odd than an enlisted man was writing a letter to a colonel. Perhaps G.N. Johnson is Field & Staff or he could be a civilian advisor/adjutant. He may be a personal friend. From his writing style, I assume he is fairly well educated.
He mentions "the General". Roley McIntosh, uncle of Chilly, was called "the General". Roley died in Texas in 1863, if I remember right. Don't know if this is a reference to Roley but it caught my attention. I'm wondering who else he may have refered to as "the General". Cooper wasn't a brig general yet. He may have been referring to Chilly or D.N. as "the General".
Considering the date... I don't think they were anticipating a fight at Honey Springs (July 17) which was a Federal surprise attack. He may have been anticipating an attack on a supply train from Ft Scott or on Ft Gibson. There were always a number of grandious ideas about capturing Ft Gibson, or raiding into Kansas, or even capturing Ft Scott.
Email the jpg and I'll post it on the messageboard.