Just to be clear: The Warmaster the Warhammer 40,000 novel by Dan Abnett not The War Master the Doctor Who audios starring Derek Jacobi. Bloody enjoyable confluence of nerdy events to have both of those come out within a week of each other but a bit difficult for casual discussion.
There is a moment of pure fan service very early in the novel where Commissar-Colonel Gaunt ends up reciting the names of troops under his command who have died who meant something to him. Not to spoil the circumstances but Abnett uses the moment to remind us that, against all regulation, Gaunt cares about his regiment.
He mentions all the names you'd expect him to like Dorden, Chief Soric, Caffran, “Try Again” Bragg, MkVenner (yeah, right, as if I believe he's dead for a second) but also characters he barely interacted with like Merrt and names I don't even remember. Its obviously written to be fanservice but Abnett is smart enough not to use it only for fanservice. It tells us something new about Gaunt: that the affection he clearly has for his inner circle isn't the extent of his affection for the regiment, he feels all the deaths even of people we don't know that well. Its easy enough to guess that he'd miss Corbec or Bragg, people we the reader knew and liked, or even someone we didn't particularly like but knew well like Feygor but that he cares about someone I either don't remember like Rilke who the internet informs me was a sniper but I don't recall him at all.
Its a good reminder that we don't know everything about Gaunt's interior life, that he has more feeling than we've been privy to even fourteen books into the series.