Waterloo—finally facin’ my waterloo

Yes, I’m an Abba fan. So sue me.
But the point of this post is my finishing the last remaining Sharpe’s novel, Waterloo (though it wouldn’t surprise me if Bernard Cornwell fits in another retcon eventually). I found it excellent, and quite suspenseful, which is really remarkable given that I already knew how the Napoleonic Wars came out.
How do you make history suspenseful when it’s already written? Thinking about the book, several elements are visible:
•My lack of knowledge. I didn’t know the details of how England triumphed over France so when Napoleon pours his troops against the British lines, I’m wondering as much as they are—how will England survive?
•Fictional characters. I know the Duke of Wellington isn’t going to buy it, but what about Sharpe and Harper? If I hadn’t already read the follow up Sharpe’s Devil, I’d have seriously worried that Harper was going to buy it (his blithe assurances to his wife that of course he’d stay out of danger just screamed cannon fodder). And several supporting characters do indeed bite the dust.
•Other issues. Along with the battle, Sharpe is also trying to settle issues with his faithless wife’s lover and recover some of the money she stole. That outcome was in doubt—and, in fact, it didn’t work out anywhere near the way I expected.
•Good writing. Obvious, but it shouldn’t be overlooked. Cornwell does a great job.
One tactic Cornwell doesn’t use, but others have, effectively, is to create a fictional challenge to the way history turns out. For example, Day of the Jackal, in which an assassin sets out to take down General deGaulle in the sixties; The Tall Target, with Dick Powell trying to stop a pre-Booth assassination of Abraham Lincoln; the film 36 Hours, in which the Nazis try to trick plans for D-Day out of James Garner; and Katherine Kurtz’s Lammas Night, in which Britain’s witches try to stop Hitler’s plans for a cross-channel invasion.
Of course, we still know how the history is going to turn out, but giving us a nonhistorical plot allows for more flexibility: History tells us how D-Day went, but we’ve no idea how James Garner will figure out the Nazis’ Mission Impossible-style tactic (convincing him it’s five years later, he’s lost his memory—perhaps if he recalled what he was doing back before that terrible accident …).
History. In fiction there’s a lot you can do with it.