Isstvan V, Drop Site Massacre
Battle of the Coronid Deeps
Battle of Beta-Garmon
Battle of Molech
Horus was the one who plan and made most of the tactical decision in this list
Certainly. but as mentioned I haven't read Solar War so I can't comment for or against him keeping the fleet functional is anything more than charisma, at which point he's got a very significant advantage in forces.
Beta-Garmon also looked like overwhelming numbers at work, if the defenders saw it as a foregone conclusion I don't get much a sense it was because of Horus' intellect that he won.
I'm aware he's well portrayed in the Black Books, but I mostly meant in the BL products, so I don't count his battle in the Coronid Deeps.
Considering how fantastically inept he was portrayed as in Vengeful Spirit, I'd be surprised if anyone could have lost Molech with his level of resources.
Isstvan III was fine but doesn't strike me as especially out of the box thinking. Same with Isstvan V.
That leaves Prospero, which I'll grant was a very elegant solution to a potentially enormous problem.
What I mean is that you hear a lot about Horus' genius but in-series he rarely does anything that makes me go "wow, never would have thought of that." Contrast, for example, Timothy Zahn's works in the Star Wars EU. They're always a joy to read because both sides of a plan are acting rationally and frequently using intuitive and obtuse thinking. Not so much with Horus, who wins engagements handed to him on a silver platter before everyone exclaims how genius it was to deploy his troops in an obvious manner.
Just my 2/5ths of a nickel.