In a letter (#323) written to Clark Ashton Smith, on July 23, 1935 we learn:

Sent a three-part serial to Wright yesterday: “Red Nails”, which I devoutly hope he’ll like. A Conan yarn, and the grimmest, bloodiest and most merciless story of the series so far. Too much raw meat, maybe, but I merely portrayed what I honestly believe would be the reactions of certain types of people in the situations on which the plot of the story hung. It may sound fantastic to link the term “realism” with Conan; but as a matter of fact — his supernatural adventures aside — he is the most realistic character I ever evolved. He is simply a combination of a number of men I have known, and I think that’s why he seemed to step full-grown into my consciousness when I wrote the first yarn of the series. Some mechanism in my sub-consciousness took the dominant characteristics of various prizefighters, gunmen, bootleggers, oil field bullies, gamblers, and honest workmen I had come in contact with, and combining them all, produced the amalgamation I call Conan the Cimmerian.

Another interesting letter (#328) to H.P. Lovecraft, December 5, 1935 tells us:

The last yarn I sold to Weird Tales — and it well may be the last fantasy I’ll ever write — was a three-part Conan serial which was the bloodiest and most sexy weird story I ever wrote. I have been dissatisfied with my handling of decaying races in stories, for the reason that degeneracy is so prevalent in such races that even in fiction it can not be ignored as a motive and as a fact if the fiction is to have any claim to realism. I have ignored it in all other stories, as one of the taboos, but I did not ignore it in this story. When, or if, you ever read it, I’d like to know how you like my handling of the subject of lesbianism.