If you're willing to do memoirs, Grant's are fantastic. Same with Caesar's war dispatches. March of the Ten Thousand is also a classic. Arrian's Campaigns of Alexander the Great has what you're looking for.

Unfortunately, I wouldn't call any of those niche topics. By rule, the more famous the commander, campaign or battle, the lesson niche it's probably going to be. I also tend to like the classics, so if you're looking for an overview, someone else probably has better recommendations.