Did Gene Roddenberry (or anyone else closely involved with production of Star Trek) ever indicate whether the show - mostly as a concept, but at least specific episodes, were influenced by "Heroic captain" type wet navy books? (I mean stuff like Horatio Hornblower, Master and Commander etc..)
Yes. In The Making of Star Trek (by Stephen Whitfield), the comparison to Horatio Hornblower is made several times. I read the book in the 1970s and had never heard of Horatio Hornblower at the time, so I had to ask my Father about him. And since my Father was an old Navy man, he wanted to find copies of the Hornblower books for me to read -- but he had trouble finding them at the used book stores he loved to browse in.