Explain the last paragraph of this chapter

"The youth, turning, shot a quick, inquiring glance at his friend. The latter returned to him the same manner of look. They were the only ones who possessed an inner knowledge. "Mule drivers-- hell t' pay--don't believe many will get back." It was an ironical secret. Still, they saw no hesitation in each other's faces, and they nodded a mute and unprotesting assent when a shaggy man near them said in a meek voice: "We'll git swallowed."

The two young men know they've received accolades for their performance and are now being sacrificed for the greater good because they're considered expendable. They have a few people to prove wrong, but they'll keep it to themselves in order to keep morale up.