One of the best, and executed to perfection! You can sort-of-see the point coming for a long, long time in the book, as he gradually builds the suspicion by dropping the occasional hint here and there, but it's always so that it must remain a highly uncertain speculation until he drops the reveal. Just the right balance between "How should I have suspected that?" and "Those hints were too much on the nose!".
Its such a crime - of war and all else, its like a blindspot of imagination. That a man would do such a thing - to what is essentially family, as tactics.. the horror..