In Chapter 8, Catherine gives Henry a chain with a Saint Anthony charm for protection on the front. This is, of course, a direct allusion to Saint Anthony, the patron of lost things:
I undid the clasp of the gold chain and put it around my neck and clasped it. The saint hung down on the outside of my uniform and I undid the throat of my tunic, unbuttoned the shirt collar and dropped him in under the shirt. I felt him in his metal box against my chest while we drove. Then I forgot about him. After I was wounded I never found him. Some one probably got it at one of the dressing stations.
Saint Anthony is colloquially known as the patron of lost things: the saint himself lost a book of psalms, prayed to God, and found his missing book after all. A prayer to Saint Anthony is supposed to help one find things that one has lost. Perhaps Catherine believes this token will protect Henry from being lost himself, whether geographically or spiritually. However, there is also irony in the fact that Henry ends up losing the necklace after getting injured, demonstrating his indifference toward religion.
The novel also brings the charm of Saint Anthony to life in Chapter 8 through personification:
She was unclasping something from her neck. She put it in my hand. “It’s a Saint Anthony,” she said. “And come to-morrow night.”
“You’re not a Catholic, are you?”
“No. But they say a Saint Anthony’s very useful.”
This passage treats the Saint Anthony charm on the chain as a real person. Henry refers to the charm as “him” and describes how he can feel him under his shirt. Even after (ironically) losing the charm, he describes it as losing “him,” as if the charm is a real person with whom he can converse. However, the personification is quickly undone by the last sentence of the passage, where “some one probably got it at one of the dressing stations.” Immediately, once the chain is out of his possession, the “he” reverts to an “it.” In order for the charm to come to life and work as a protection, it must be in a person's possession. This suggests that the true value of the charm isn't necessarily a literal ability to bring back lost things but the emotional comfort it brings the wearer.