Every time i see "this will all be over by Christmas" in the Captain's diary entries, it's yet another gut punch, another twist of the knife. He was so hopeful, it just breaks my heart. He had no idea.
This
Exactly this!! In the audiobook, you can hear it in his voice with the entry from when Havers left. He doesn't believe it at that point, he's clearly faking it, and the combined anguish of Havers leaving and losing faith in... kind of everything, arguably, makes him just tear the page out. It's tragic because he so desperately wants it all to be over and done with, and he wants to help, but he feels powerless because no one will let him help and he ultimately can't for one reason or another, so he has to rely on those deemed more important than him but the need to maintain that faith when he wants to do more is painfully impossible.
And the last diary entry the Captain has, a whole 4 years after Havers left, he's finally admitting "It won't be over by Christmas, will it?" He's finally worked up the courage to bite the bullet and commit to writing out the big fear at play. 4 YEARS!! At long last, he's able to give in to that doubt and write it down permanently.
There's something so horrific and pitiful about that deterioration of the Captain's faith. He can't be idle and happy simultaneously, as seen in "Gone Gone", so being forced to do something seen as idle and cowardly work during a time meant for bravery just eats at him, chipping away at his hope and resilience for years. Even though his work is ultimately useful, he doesn't really get to reap the rewards, he doesn't get to see it in action, he doesn't get the glory of battle that's seen as social capital for him and his ilk.
He's stuck watching time pass him by while he feels like he's contributing nothing. He did it in life, and now he's stuck doing it in death.
The Captain is someone who believes in structure and systems, but when he's forced to question the fairness of these systems he's been told are always fair, he falls apart. He needs to do something or he starts thinking. "But if I stop, then..." Then he starts thinking and crumbles. Wartime forces him to confront how much faith he can put in others committing violence and really the whole prospect of war (as I see it), which are things he's been told are necessary. And after a point, he's stopped seeing what it's all for, only now he has to fake that trust in higher people. "I try to remain positive, but it's getting terribly hard." He's an optimist who's losing a reason to be such.
"(If we even get that far!)"
"This wretched war."
"When will it end? 1948? 1949?"
"Will life ever be the same again?"
He's doubting. A creature of faith and habit is doubting because there is too much room for uncertainty at a time when no one can afford it.
He's stopped believing. That's exactly it.
