LitCharts assigns a color and icon to each theme in The 5th Wave, which you can use to track the themes throughout the work.
Trust and Belief
Survival and Perseverance
Warfare and Dehumanization
Family
Summary
Analysis
In the present, Cassie can’t stop thinking about the Crucifix Soldier. He wasn’t Branch or Vosch, but all of the soldiers blend together to her. She thinks again of Sammy in the school bus. She wonders if the military “rescue” was all a ploy to get ahold of kids like Sammy, and she tries to figure out what they’d do with all those kids. But if the Others really wanted children, they didn’t spare them in any of the previous waves. Cassie vows to keep standing as humanity’s last warrior, if she really is the last human.
This passage emphasizes all the different ways that Cassie lives in a state of uncertainty. On the one hand, she can’t tell who’s a friend and who’s an enemy because on the surface they might all look the same—and even if she can identify an enemy, she doesn’t know what their ultimate plan is. In addition to capturing the confusion that would result after the collapse of society, this passage also captures the difficulty of figuring out one’s identity while growing up, especially during such difficult times.