Thanks Tribble puncher and CeJay. I'm really glad you both enjoyed this one.
I took Cartwright's involvement with Section 31 from Trek Lit. I think it made sense and I like Section 31, so I thought why not? I also saw similarities in Admiral Cartwright and Into Darkness's Admiral Marcus so I thought it would be neat to have Cartwright as Marcus's protege and also the man who brings him, via his wife Alice, into Section 31.
Cartwright is a villain in Star Trek 6, but I think his motivation wasn't completely unreasonable. I wanted to explore where his hard feelings for the Klingons might have started or became even more hardened so that his betrayal in Star Trek 6 comes from decades of fearing and maybe hating the Klingons. And he has the destructive Four Years War as a memory, informing his decisions and that shaped his view of the galaxy. But also from a desire to defend the Federation at all cost.