Moroni’s second tactic is a decoy and ambush. To lure a significant portion of the Lamanites out of Mulek, he sends Teancum with a raiding party down near the seashore. This party had to be sufficiently large to be a threat, but small enough that the Lamanites could easily mount superior numbers. The most convincing target for Teancum’s raid would most likely have been the fields, not the city. The Lamanites would know that such a small force could not prevail against the fortified city, but the Nephites could burn and/or capture their food supply, thus reducing the Lamanites’ ability to survive.
Thus, although Mormon gives no details about the timing of the raid, it had to occur after planting season, which would have been roughly the same as the rest of the northern hemisphere. The Lamanites took Mulek in the twenty-fifth year (Alma 51:26, 37), and it is retaken in the twenty-sixth year (Alma 52:1). With a new year occurring in February, that suggests that this raid occurs late in the year when the fields had already have been sowed and it was late enough in the season that damaged crops could not be successfully replanted.
To protect their food supply, the Lamanites must respond to Teancum’s threat; but they obviously do not expect Moroni’s accompanying tactic: a night march. Night marches were rare. The lack of light and combination of dense vegetation combined to make the way more difficult when marching in areas where there were no roads. While some roads linked some cities, most Mesoamerican travel was over unimproved ground. This unexpected move put Moroni’s army much closer to Mulek than the Lamanites would expect.