Final answer:
The narrative technique used in the excerpt is foreshadowing, which is used by Ken Burns in documentaries like The Civil War to create anticipation and keep the audience engaged by hinting at future events.
Step-by-step explanation:
The narrative technique described in the excerpt appears to be foreshadowing. Foreshadowing is employed by Ken Burns in documentaries such as The Civil War to suggest that major changes or developments are imminent. This technique is particularly effective after emotional peaks in the narrative to keep the audience engaged and to build anticipation for what is to come in the story. Ken Burns is known to deliver such warnings through his narrators, which creates a mood that indicates to the audience that there are more developments ahead, thus maintaining their interest.
By signaling that things are not as they seem, or that significant shifts are on the horizon, foreshadowing increases the suspense and compels the viewer to continue watching. This technique is integral to documentary storytelling, it evokes curiosity and maintains a consistent level of engagement with the audience, fulfilling a similar function that it would in fictional narratives.