In "The Monkey's Paw" what does Jacobs mean when he writes "on the husbands face was a look such as his friend the sergeant might have carried into his first action." Is a "first action" some sort of military term?
This instance of W.W. Jacobs's short story "The Monkey's Paw" comes at the poignant moment in the story when the representative from Maw and Meggins has to disclose to the Whites the horrible news that their only living son, Herbert, has had an fatal accident at work, and that he is dead.
From the beginning of the story we learn that the Whites are quite attached to their son and, for this reason, the news are extremely hard to take. This is why the author describes the scene as one where the shock of Herbert's parents permeates the room and leaves an image of horror, fear, disbelief, denial and astonishment that would have resembled that of their friend, the Sergeant-Major, during is first call of duty as a soldier.
"I beg that you will understand I am only their servant and merely obeying orders."
There was no reply; the old woman's face was white, her eyes staring, and her breath inaudible; on the husband's face was a look such as his friend the sergeant might have carried into his first action.
Hence the "first action" does refer to a moment of impossibility where you lose control of everything and, yet, you are expected to continue to operate as usual. Mr. White, as we know, is trying hard to keep his sanity and as best as he could tried to just say "it's hard".