The Nephites could not prevent the raid on Ammonihah, but they could attempt to do damage to the Lamanites as retaliation. To do so, they go to Alma as the high priest to receive knowledge of where to search for the Lamanite army. Alma consults Jehovah, and receives the information on the path that the Lamanites were taking. Most Lamanite invasions came from the south through the pass near Manti, which was near the headwaters of the Sidon. This Lamanite army may have bypassed Manti, but ended up on the same basic path.
The Nephite army heeds Alma’s word, and finds the Lamanite army as promised. They were able to recover the captives even while the “Lamanites were scattered and driven into the wilderness.” The appearance of the captives as a motivation in this story occur multiple times. Captives are mentioned as part of the Lamanite attack, then as a reason to pursue the Lamanites, and finally as a culmination of the Nephites following Jehovah’s information, and recovering the captives as Jehovah had promised. Captives are important to the story for reasons that we will see again as part of the story of the Anti-Nephi-Lehies.
At this point, however, the return of the captives highlights Jehovah as God of the Nephites, and as a God directly involved with his people.