Moroni comes up with a strategy that will lure many of the Lamanites out of the city 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 question is the type of threat. While the march comes along the seashore, it is probable that the threat was against the fields, not against the city. The Lamanites would know that such a small force could not attack the city, so they were safe. The only incentive to leave their protection would be to protect something else, and that would likely be their food supply. It would be an effective tactic for the Nephites to destroy the crops, and therefore the ability of the Lamanites to survive for long.
For this to have worked, the attack had to have taken place after planting season. Once again Mormon does not give us the timing of the events within the year. The retaking of Mulek will occupy a year, so it is not unlikely that this feint has begun after the sowing of the fields.
The second aspect of this plan that allows it to work is a rare night march for Moroni’s force. Night marches were rare because there was a lack of light, and therefore marching in areas where there were not roads was much more hazardous. This was an unexpected move, and placed Moroni’s army much closer to Mulek than the Lamanites had supposed.