At what point in the book does Stephen have a epiphany?

Stephen, one of the protagonists of Sebastian Faulks's novel Birdsong, is an English soldier fighting on the front lines during World War I. In the course of the narrative, he experiences various traumas, including witnessing the death of his closest friend and losing the love of his life.
At what point in the novel does Stephen have an epiphany? It happens in part 1, when Stephen pays a visit to a cathedral. He is not a religious person; but in the church, he foresees the terrible devastation that the war will bring, and he glimpses the personal tragedy he will face:

He saw a picture in his mind of a terrible piling up of the dead. It came from his contemplation of the church, but it had its own clarity: the row on row, the deep rotting earth hollowed out to hold them, while the efforts of the living, with all their works and wars and great buildings, were no more than the beat of a wing against the weight of time.

Stephen's epiphany in the church speaks to the human toll that a war takes. The presentiment of tragedy is sobering. Imagining or even expecting the "terrible piling up of the dead" and the knowledge that the dead could include one's own friends or, indeed, oneself, is enough to make a non-religious man walk into a church and begin to pray. Stephen prays to God:

Save all of us. Save me.

But in this moment of epiphany, Stephen seems to know that even God can not save humans from suffering at each others' hands.