Final answer:
A flashback is the literary device used when a narrative goes back in time, like Luttrell revisiting an operation in Afghanistan, to provide background or context for the present story.
Step-by-step explanation:
The literary device used when Luttrell goes back in time to an operation in Afghanistan is known as a flashback. A flashback is a plot device where the narrative shifts back in time to show events that have taken place before the current point in the story, providing background or context to the present situation. This technique can enhance understanding of a character's motivation or the events leading up to the current action. When employed effectively, a flashback can add depth and complexity to a narrative. It's common in both literature and film as a way to reveal the past that shapes a character's present and future.
Authors often switch tenses to indicate the shift in time, from past to present or vice versa. Additionally, historical material may provide a backdrop, placing fictional characters in factual settings which can make the story more engaging while still remaining historically accurate. The key is seamlessly integrating the flashback so that it feels natural and provides meaningful insight.
Repetition of certain elements or motifs in a text, like in F. Scott Fitzgerald's The Great Gatsby, might indicate important themes or symbols. These devices serve as cues for the reader to pay special attention to certain details which could be crucial for the understanding of the story's message.